Equipment suggestions for live viewing

[London_David]

Hi,

I'm new here and this is my first post... and is now also my second post. I was asked to re-post to here from the "starting imaging" section -  the first version has a bit more detail about the logic behind my shortlist. 

So -- I'm looking to purchase an observing/imaging set up. I would like to get:

 

• OTA
• Mount
• Camera

 

My goals and constraints are:

 

• DSO observing. I like observing the moon too, but DSO interest me more than anything else.
• Primarily I want to do live or close to live viewing. To me that's from live video to 10 second auto stacking. Ideally 5 seconds or less per frame.
• Occasionally I'll do some visual observing, but that's less important.
• I have no space in my apartment, so it can't be a big scope. Size wise I'm looking at 150mm reflector, 80mm refractor, 5/6"SCT kind of range -- and as light as possible.
• It needs to be vaguely portable and packable into an Uber.
• I live in Zone 2 London so I need to cut through light pollution.
• I don't care so much about making pretty pictures, I just want to see objects in colour and good resolution - I don't have a huge interest in competing with Hubble using photoshop. At least not yet.
• Budget is about £1500 for the basics of OTA, mount, and camera. But it's flexible. I feel more constrained by space and light pollution. I don't want to waste money on expensive equipment that can't be used because I can't get to a dark area, but I'd spend more if I was convinced it was going to give me a radically better result.

 

My OTA shortlist:

• Skywatcher Explorer 150PDS or 130PDS
• Altair Astro 70ED-R
• Celestron NexStar SLT
• Orion Starblast 6i Intelliscope
• Bresser NT150S/750
• Meade StarNavigator 130mm f7.7

My camera shortlist:

• Atik Infinity
• Starlight Xpress Ultrastar or Lodestar X2
• ZWO ASI224
• GSTAR EX3
• Malincam Xtreme
• Sony A7s
• Maybe a mono camera with motorised filters. Open to suggestions.

My mount shortlist:

• Skywatcher Star Discovery AZ Goto
• EQ3Pro
• Whatever is in the bundle with the telescope.
• Something go-to or push to. 

 

A bit of quick background -- this is my first setup but I've worked professionally as a cinematographer, so I know lots about digital cameras, optics, collimation, image processing, photoshop and tech etc, but I'm relatively new to astronomy. I have put in a few hours using my dad's 8"SCT for visual observing.

I know the Sony A7s and am okay with the noise up to about ISO204800 at ISO409600 it's a bit noisy for anything except composition. The A7s @ ISO128000 would be very acceptable noise levels for me. My back of envelope calculations suggest an Attik Infinity can shoot at about what seems like ISO6400 with low noise. I have no idea if that is correct, or how it performs at much higher gains. How would the A7s and the Infinity compare? 

I'm curious - but not sure about - mono imaging with a motorised filter. Is it better to spend £450 on the camera and the £450 on the filter wheel, or £1000 on a colour camera. 

For the OTA, the Skywatcher 130pds and 150pds seem to keep jumping out at me, recommended from several places independently.  The imaging newtonian seems to fit a sweet spot for me and I'm leaning towards that. But what size? Smaller and lighter are big advantages for me. 33% less light for the eye isn't much since it's less than half a magnitude for visual --  but what does that mean for imaging 33% longer exposures? I could do the maths but I'm not sure how it works in terms of the quality of what you would see differently.

Some questions:

• What would you recommend in that equipment?
• What would you avoid?
• Filter/eyepiece/accessory recommendations are welcome!
• Am I missing anything obvious?
• Am I thinking about this set up in the right way?
• There's a lot of cameras and manufacturers out there -- what's the best camera for what I seem to be looking for.

 

Thanks!

 

 

[stash_old]

Although not needed for VA I would still say,IMHO, spend the most on the mount - just in case you change your mount!  Maybe an Neq6 if finances allow.

[Martin Meredith]

Hi David

Just some opinions on a setup that works for me:

Camera. Several of us here (as you may be aware) use the Lodestar (mono or colour) because it is sensitive and has excellent easy-to-use yet powerful and free StarlightLive software developed by Paul81, an SGL member. This software also works with the Ultrastar.  Software is a huge part of the equation for me, and can make or break the ease of observing live. I've been using it for almost exactly 3 years during which time it has evolved a lot, and it really makes EAA a pleasurable experience. I also see some great results from the ZWO CMOS family of cameras. Their lower read noise means you can get away with shorter exposures, which can add to the live experience. In the end though it is necessary to collect photons to reduce intrinsic noise, so sensitivity and pixel size remain key things to look at. Based on the typical seeing you can expect at your location, you can work back to the maximum resolution you need (this is also intertwined with the scope decision).

Take a look at some of the images posted here, and also the EAA object of the month series on the Cloudy Nights forum, where you can see results from these and other cameras on the same objects. You have to take into account the different sky conditions reported too of course. My suggestion would be to look at those before deciding on a camera.

Mono vs Colour. I'm also a big fan of mono+filters because of their flexibility (e.g., more efficient in the use of narrowband filters) and to my mind more accurate colour rendition. That's probably a minority opinion for EAA-style use, but that might change when more software supports live spectral combination. Note that a filter wheel adds non-trivial weight to the setup, so you need to take that into account when thinking of a mount.

Scope. You mention quite a range of options here. It is worth exploring FOV calculators to see what different objects are going to look like in each of these. A 70mm refractor is not going to behave like a 150mm reflector. I know a lot of people swear by the 70-80mm range for AP, but I have my doubts for general-purpose EAA usage. A lot depends on which DSOs are of most interest. No one scope is perfect for every type of DSO. Some of the brighter and bigger open clusters don't fit in my field, and neither do some of the bigger dark and bright nebulae, nor the larger galaxy groups. At the other extreme I could sometimes use more detail on compact galaxy groups. It is a tradeoff, and 500-800mm focal length seems a reasonable place to be.

I started out with an achromat and grew to dislike the star bloat. This can be reduced with filters, but not entirely removed. Now I use an imaging Newt mainly. Speed I'd say is of the essence. If I had to replace my 8" f/4 it would be with another 8" f/4. Since weight is one of your criteria, you might want to check out the 6" f/4 models available from various suppliers, including TeleskopService. That said, an ED quality refractor is also a viable option, but make sure you check whether you are severely under sampling using a CCD suitability calculator, otherwise there is a danger of blocky stars.

I hope others will comment on the SCTs and Mak-Cas options as these are also popular and perform well for EAA.

Mount. As for the mount, I have one that can be used in EQ or alt-az but I have never used it in EQ mode. If I someday get a permanent pier I may do so, but I haven't felt the need so far. Unless you want to future-proof against doing guided AP, an alt-az mount is perfectly fine for EAA now that modern software handles field rotation during stacking.

Weight. It may pay off to buy a carbon fibre tube scope if available if it helps to keep the mount category down, as you save weight not just the scope but the mount too.

Accessories. I'm fortunate to have reasonably dark skies (SQL 20.5 at best) so I operate without light pollution filters, but I imagine others will make some suggestions here. If you do go down the imaging Newt path, I recommend investing in a decent autocollimator. A Bhatinov mask is more or less essential to make focusing a 20 second task. Imaging Newts also benefit from various tweaks which I can go into if you decide on that route....

Feel free to ask more. I'll say again, these are just opinions!

Martin

 

 

[Robrj]

For any kind of imaging, you can take any manual option like the push-to scopes off the table.  For visual observing, they're great but for video astronomy or imaging, you need something that tracks.  A goto dob might be an option but there are better choices if you don't already have one.

You have quite a variety of options; some really expensive and some cheap.    It might help narrow down your choices if you gave us an idea of an overall budget.

 

[Macavity]

It's been a while... but I would certainly commend a fast Newt
with a fair bit of aperture? Ideally an 8" f/4 on an HEQ5. Include
e.g. a Lodestar X2 and you are already at your budget. It will take
up a fair bit of space too and is not overly light weight! <sigh>
But (as noted above) such would be (was) fairly future proof.

OTOH, I have seen favourable reports re. smaller 6" f/4 Newts!
On a lighter mount --EQ5 certainly (EQ3-2 maybe)? I never had
lot of success with smaller refractors (e.g. ST102 f/5 Achromat)
re. VIDEO astronomy. They make fine rich field scopes though!
Small APOs are nice, but are smaller / slower... f/6, f/7 etc. They
will image bright open/globular clusters, but galaxies & nebulae
always seem need a bit more... Oooomph (aperture + speed!)  

Note: Fast Newts are not of "Astrograph" quality out of the box.
But not aimed as such. I see them as "Video Light Buckets"...

[Dave In Vermont]

Chris, above, hits the nail straight on - a 200mm F/4 Newt isn't optimized for perfection in Video-AP right from the box. But no telescope truly is. One will always find any scope can use a tweak or nudge this way & that. And this will need something a little this-way, or that, as your aims change. But a 200mm F/4 makes a good choice for an initial instrument. And often without the added cost(s) of being called "astrograph."

We used to call them "Rich-Field" telescopes. Then the focuser was swapped-out from 1.25" and to a 2" model. And the tube was extended (or the primary was changed to F/3.9) so the focuser was further back on the tube. The - Ta! Da! - the "Astrograph" was born.

Onwards & Outwards -

Dave

[London_David]

@Martin Meredith

Many thanks! That’s all very useful. I've just been going through the things you talk about and it looks like I started by looking at the wrong forum areas…

The image you posted showing the star forming regions of the fireworks galaxy have sold me on multispectral mono imaging. I had no idea you could do that with live stacking!

I still want to start easy though: observing under 10s sub frames. Is that realistic? Pretty much everything on EEA object of the month seems to be 30s + exposures. Not that I need to get object of the month, but I'd like to see something...

I like the look of Telescope Service 150 f4 in carbon fibre at €850. This: (https://stargazerslounge.com/topic/237346-f4-or-f5/) puts me off anything less than f5. With an f-stop<5 Am I likely to have to do a tricky collimation regularly during a session? 

Also, I've read lost of good things about the Skywatchers. What are the TS scopes like? 

On the Lodestar/Ultrastar with filter wheel - I am guessing comes to just under 1kg. I have read some stuff about the focusing on some Crayford scopes slipping with weight. Have you had any issues like that?

And finally... Would a vixen flip mirror work on this kind of set up or does that cause issues with focus?

Lots more questions too as I figure things out! Thank you so much for the help!

Thanks,
David

[London_David]

@stash_old

Unfortunately storage space won't let me have a larger mount! Truth is I barely have space for a smaller mount... I'm going to have to do some packing or put stuff in storage, and even then... Also -- I was under the impression From Martin and a book I read that, while you are totally right I should have a better mount, under 30s exposures you can get away with (though I understand some might get dumped due to vibrations etc). 

 

 

[SmokeyJoe]

Interesting, informative answers. I have just asked a similar question in the 'getting started' section (think it might be in the wrong place) but many of my questions have been answered here, now wondering wether to swap my sw200p (EQ5 goto) for a smaller PDS version or my colour CCD for a mono.

[London_David]

@Robrj

Some of this is in my earlier original post so apologies if you read that... but basically I have a vague budget of £1500 for camera ota and mount. But that's flexible. If i need to spend more to get what I think interests me I'll do it. A quick back of envelope calculation I did looked to be about £2.5 for Martin kind of pointed me in the direction of. I'm fine with that number but... I'm wary of just buying everything without testing it out since it wouldn't be the first time I've bought more expensive camera gear than I really need. 

So the Dobsonian was/is a way out from all of that. Cheap, easy, grab and go and able to fit in the cupbaord. I do want a telescope and this is maybe good enough. I'd stick a cheap low light Mallincam or something on it and be done for a little over £500. If I don't image much other than the moon, for £500, I'd be okay with that and mainly use it for visual. But of course it's not what I really want. 

The refractors, were to me the obvious answer for imaging since that's what I see a lot of photos taken on. I had always had the impression that for astrophotography refractors were still the best unless you got into things like big truss RC scopes.

Also... its basically a massive new lens for my camera and I know and love those so that makes sense. I have tripod mounts already that will work. I can put it in a backpack and use it for long exposure or just visual. They also appeal a lot because they're wide field for DSO and relatively small. That does still appeal. Size and light pollution are my biggest constraints.

That said -- 

Thinking through the responses here, I'm pretty sure a Newtonian Imager is what will suit my interests most.  

You see, until a few weeks ago I had thought I would never get any dso viewing at my location, but then I saw some stuff by people apparently in a very similar location. So it is possible it turns out. However -- I'm still not quite sure if where I think I can set up will actually give me a good enough view up when I have close buildings.

The fall back position on the Newtonian is... if the imaging doesn't work that well... I can still use the Newtonian as a more powerful visual telescope than any refractor in the price range. But... if it's just going to be mainly visual, a carbon fibre tube and the rest starts to seem excessive.

So if I seem schizophrenic in that list it's because of the combination of those trains of thought...

Does that make sense? 

The core thing I'm trying to grapple with on scope choice is: I have a poor viewing location and I'm inexperienced, so will spending extra for performance get results in worthwhile observation or is it going to be an exercise in frustration?

I don't know if that can be tested without purchasing a lot of equipment though...

This is why I'm edging towards a 150mm Newtonian. It's what I think I want, even if space is an issue. 

[London_David]

@Dave In Vermont

Yes -- I think the Newtonian is the way to go -- but I can't do 200mm it's frustrating but it's just too big. 150 is really pushing the limit of what I have space for.

Does anyone know anything about how good the TS Optics 6" f4 carbon fibre made in Germany is? Is it the same optics as their GSO one with a German installed cf tube?

[London_David]

Martin mentioned the ZWO cameras -- does anyone know the zwo ASI1600mm performs with live stacking at short exposure. It it sort of equivalent to the Ultrastar? I've had a look around and I can't see anything.

The images you see are spectacular, but all massively long exposures...

[Macavity]

It's often hard to FIT scopes / mounts within a "modern lifestyle"?
I know well the limits of both budget & space (not to mention age)!

But [IMO] TS (Probably re-branded GSO) Newts are [IMO] excellent. I note too that sadly the price of this stuff seems to be creeping up. I paid £400 for a 8" f/4 Steel Tube  via "Bern at Modern Astronomy" Dealing with TS in pretty much the same as with more local dealers. But I have been happy with my "TS" Newt re. for a number of years. Re. Video Atronomy, I suppose the way I look at it is... What are the budget alternatives available re. fast-ish optics & large-ish aperture? But we all know the price of top-end APO's and fast Camera lenses.

The difficulty of collimation in Newts is (most likely!) related to the "cube" of the f-number. So, in theory, f/4 Newts are "twice as hard" to collimate as f/5 ones. However, many beginners buy the LATTER and seem to manage? Or else they survive with poor collimation! A problem shared by a LOT of Newts is poor springs on the primary mirror cell. (Lesser issues with the secondary?). BUT, at the level for Video Astronomy anyway, I found that a "Strong Spring Mod" (qv) was adequate for my fast Newt. I bought "Bob's Knobs" too...  

I don't like to "proscribe" people on forums (lol!). But our friend
Laser_Jock may still own one of their 6" TS (GSO) f/4 Newts???
His ideas for improving the primary "spring-age" were invaluable! 

https://stargazerslounge.com/topic/285166-cheap-f4-reflector-am-i-crazy/?do=findComment&comment=3123169

To an extent, Video Astronomy needs modest "down & dirty"?
But you seem good at research, and anticipating the issues... 

[Macavity]

As a final postsript (honest!): I think it fair to say that one of the
advantages of an f/4 scope (at 200mm) is that the focal length of
(800mm) is "about right" (30' x 20' on 1/2" chip) for most DSOs!

If you are going to a 6" scope, you could well relax the speed to
a more standard f/5 (f=750mm) and get almost the SAME field!
To go faster, you can experiment with a budget focal reducer...
until various aberrations become totally beyond the pale!

[London_David]

@MacavityInteresting... though f5 to f4 would theoretically take 1/3 off exposure times. I wonder just how much I would notice that. Is it £500 worth? A budget reducer isn't a bad idea if I want to get quick and dirty to get a sense of something then maybe take it off for longer exposures.

So, collimation -- I'm not too worried about that to be honest. I've done plenty of that kind of thing before with projectors, movie cameras and stuff. Not quite the same but fiddly, getting lines to match up and avoid interference patterns stuff. It's only going to annoy me if it is something that is going to slip in the middle of a session. Having read around I assume that's not going to happen with a decent scope (though that post I saw earlier did make me wonder).

Size wise 200mm is just out of the question for me. 150 or even 130 is better. Which after all this points me in the direction of...

-- Skywatcher Explorer 130pds  750mm f5 3.66kg £175

-- Skywatcher Explorer 150pds 750mm f5 4.93kg £219

-- Bresser NT150S/750 f5 5.5kg £235

-- TS 150 600mm f4 carbon fiber 4kg €849

-- GSO 150 600mm f4 5.75kg €399

-- ZWO 153 612mm f4 3.8kg carbon fiber €893

 

I'm assuming the TS scope has the same optics as the GSO. I've seen good reviews for the GSO 150 and the SW150pds. The130pds everyone likes so much there's even a dedicated thread here at sgl. Bresser I know nothing about, though the f8 version gets good write ups and it comes with a 26mm Plössl eyepiece. TS, GSO and ZWO are tube only, I'd probably buy some cheap eyepieces. 

For 1 stop, I'm not totally convinced it's worth £500+ for carbon fiber since the GSO would overload the 6kg mount I'm looking at. Though carbon fiber is cool, I also know nothing of the optics on either.

So let's assume I'm going for a mono Ultrastar/lodestarx2 and a filterwheel set up...

Anyone want to say which one they would buy?

 

 

 

[shirva]

Very frustrating trying to get the right combination,, 

What you would like, to what is practical 

Lots of us have been trying this for years, I've owned the eq3 pro for years and it's a good mount and can also be run via eqmod as well to make it better,, the smaller the scope the better it performs, I have used a 8" newt on it,, not recommend but I had extra balance weight and legs unextended in a enclosed garden, startravel 102 refractor and the ed80.

The ed80 has been overlooked as yet in the suggestions, it is a fantastic scope for the money and adding a Skywatcher 0.85 matched focal reducer/flatner makes it even better,, I use a DSLR on this combo, 600d or modded 450d and if you run your DSLR via a laptop and backyard Eos and astrotoaster ,you then have a cracking semi portable piece of kit.

 

[shirva]

To go totally portable the new

https://www.firstlightoptics.com/skywatcher-star-adventurer/skywatcher-star-adventurer-mini-sam-wifi-astro-imaging-mount-bundle.html

Looks a nice but if kit,, stick on a modded DSLR and run it from a tablet or mobile phone 

[HiloDon]

Hi David,

I thought I might throw you a bit different approach to an EAA setup.  You might want to consider a Celestron Evolution 6.  It a very stable mount and the improved drive system can give 30-45s tracking for most of the night sky.  It's a very easy to handle, portable setup.  I have mine in a medium size roller suitcase for transport. A focal reducer can get you down to f3.3.  .5 reducers are cheap and available most everywhere.  I have an MC MFR5-II that works well down to F3.  You can find them used for about $100 US.  That should be enough exposure to give good EAA views using the Lodestar that Martin suggested.  You could also consider getting a Hyperstar in the future to get down to F1.9 with a fully corrected field of 16mm, more than enough to cover the Lodestar and Ultrastar if you ever want to upgrade to higher res.

Another camera to consider is one with a CMOS 224 sensor.  ZWO has one available for about $300 US.  I just ordered a Rising Tech 224 for $168 US from the Ali Express site.  I'll run some tests with it and report back on it's performance for EAA.  Can't say much about them from personal experience, but they sound promising.

The Lodestar will allow you to do the live multi-spectral imaging you may be interested in.  I find the filters, wheel and multi stacking routine a bit too much for my taste, but others have gotten some excellent results with it.  For color, I like the OSC cams.  I have mono cams mainly for narrow band Ha views of emission nebula.

Hope this helps.

Don

p.s.  Here's a link to my gallery of albums I've collected over the last few years using this stuff.

https://stargazerslounge.com/profile/36930-hilodon/?tab=node_gallery_gallery

[Martin Meredith]

On 2/25/2017 at 22:48, London_David said:

@Martin Meredith

Many thanks! That’s all very useful. I've just been going through the things you talk about and it looks like I started by looking at the wrong forum areas…

The image you posted showing the star forming regions of the fireworks galaxy have sold me on multispectral mono imaging. I had no idea you could do that with live stacking!

I still want to start easy though: observing under 10s sub frames. Is that realistic? Pretty much everything on EEA object of the month seems to be 30s + exposures. Not that I need to get object of the month, but I'd like to see something...

I like the look of Telescope Service 150 f4 in carbon fibre at €850. This: (https://stargazerslounge.com/topic/237346-f4-or-f5/) puts me off anything less than f5. With an f-stop<5 Am I likely to have to do a tricky collimation regularly during a session? 

Also, I've read lost of good things about the Skywatchers. What are the TS scopes like? 

On the Lodestar/Ultrastar with filter wheel - I am guessing comes to just under 1kg. I have read some stuff about the focusing on some Crayford scopes slipping with weight. Have you had any issues like that?

And finally... Would a vixen flip mirror work on this kind of set up or does that cause issues with focus?

Lots more questions too as I figure things out! Thank you so much for the help!

Thanks,
David

Hi David

First, I'm glad Don has added his opinion because the SCT option might be more suitable for your situation.

If you want short subs, do consider the low read-noise cameras (e.g. ZWO), which excel at the kind of sub-length you're looking at. Personally when I'm observing even 30s seems to pass very quickly once the first sub is on the screen, but there is something special about seeing the image build up in near real-time.

In my experience, f4 Newts need to be regularly collimated even after making the mods Chris mentioned, at least if you are mounting/unmounting the scope every session as I do. I've got used to spending usually a minute or two tweaking at the start of the session and it doesn't worry me, because I prefer to know that the scope is more or less operating at its best. Even if I had an f5 I suspect I would do the same... I do it towards the end of cool-down so it doesn't eat into observing time. I never recollimate during a session, and I seem to maintain similar star shapes throughout.

I haven't weighed the filter wheel but I think that with the various adaptors and fully loaded with say 7 filters, I suspect it is a little more than 1 kg. I've not suffered any slippage that I've noticed. EAA is pretty forgiving in general. 

I have a Vixen flip mirror but I use it with my refractor when mounted on a StarAdventurer, which is non-GOTO. To be honest, mixing visual and EAA in a session doesn't really work well in my opinion because the EAA ruins any dark adaptation you ought to attain for a decent visual session.

cheers

Martin

[Robrj]

On 2/25/2017 at 13:48, London_David said:

@Martin Meredith

On the Lodestar/Ultrastar with filter wheel - I am guessing comes to just under 1kg. I have read some stuff about the focusing on some Crayford scopes slipping with weight. Have you had any issues like that?

I had a problem with the extra weight of the filter wheel causing the focuser to slip on my newt but there's an allen screw in the base of the focuser (between the adjustment knobs) where you can tighten it up.  After I tightened mine, it works fine.  I have the focuser pointing downwards for balancing purposes (eq mount) and it seems to hold without slipping and adjusts fine.  It shouldn't be a problem with the focuser pointing to the side.

[Robrj]

20 hours ago, London_David said:

@MacavityInteresting... though f5 to f4 would theoretically take 1/3 off exposure times. I wonder just how much I would notice that. Is it £500 worth? A budget reducer isn't a bad idea if I want to get quick and dirty to get a sense of something then maybe take it off for longer exposures.

I bought a 2" 0.7x focal reducer for my f/5 newtonian which brought it down to f/3.6.   Since it's 2", I mounted it to the barrel of a 2" GSO barlow (took off the barlow lens) and stuck the Ultrastar/Lodestar in the barlow.     It works great.  Since putting the filter wheel on, I took it off. 

[London_David]

@HiloDon

Hahahah. Okay. 6" SCT. And here I thought I'd settled on a Newtonian!

This sent me off another research dive. Great to have the different angle on this.

So the thing that made me dismiss an SCT originally was star smudging I'd seen in some photos. Your images are spectacular however.  So it seems smudging is entirely fixable with a coma corrector or hyperstar. 

But that 6" is heavier than I was looking at. I know this is kind of crazy thing to be a deciding factor... but my storage space is will fit a 4kg tube but probably not a 7kg one. Does the mount come off, not just the tripod but? The bigger fixed mount would be an issue.

I originally measured my space for a 5" sct which would fit. 6" I think may be too much. I'll double check the physical space again. F1.9 @ 6" would be pretty cool. But since I don't live alone, there are other considerations.

So... I think it's down to the Skywatcher 150pds, or a carbon fiber TS or ZWO at f4. 

Thanks for the camera info too -- I'm starting to get a sense of things now!

I came across a post of yours on Cloudy Nights mentioning that you thought the Ultrastar was best suited for very fast optics. That pushes me away from the SX cameras a little. Possibly towards the Atik Infinity or ZWO. Which sent me on a long dive into cmos territory. Which is my next post...

[London_David]

 

@Martin Meredith

Thanks! All very useful. I've been doing some more looking into the things you mention.

Quickly on colimation -- if it is just 5 minutes as part of the setup I'm not worried. I'm used to that kind of thing setting up projectors. 

Now -- both Dom and yourself mentioned the ZWO cameras and the more I've read the more that they seem to be well to be suited for me. However, what do people use for near live viewing. Is it AstroLive? Their website doesn't seem to be working. How is that software? From the YouTube videos it seems fine...

I assume from your original post here that the Starlight Live is the best and easiest to use software.... Or are AstroLive, Starlight Live and the Atik Infnity software all quite similar these days?

The ZWO hardware however... I'm still a little confused. 

I know full well not to compare cameras on just specs... but going just on specs... the best seem to be:

-- ASI178 -- 6.4MP, 2.4µm, 1.4-2.2e, QE: 80-85% £375 mono
-- ASI290 -- 2.1MP, 2.9µm, 1.0-3.2e, QE:? £399 mono
-- ASI174 -- 2.3MP, 5.86, 3.8µm, QE: 74-80% 3.5-6 $899 mono $599 colour
And ZWO dso recommendation:
-- ASI1600 -- 16MP, 3.8µm, 1.2-3.6e, QE:?, $999 mono, $699 colour.

(Does anybody know why the mono is more expensive?)

This is based on the following assumptions:

-- Priority is for highest QE and lowest read noise.
-- From the calculations in your post on on S/N I can use pretty short exposures (under 30s, maybe even down to 1 or 2) and not worry too much if seeing is not great. Which I figure means I don't need a cooled camera. 
-- Minimum 2 megapixels is a good image size for me, I'm used to processing video at 2k. 

Also:

--Using the seeing/pixel scale calculator, I'm tending towards oversampling rather than under sampling and when there is particularly good seeing plan to use a Barlow and shoot smaller objects.
-- On the 600mm@f4 the ASI 178 due to the pixel scale it has the best match in terms of sampling overall, with the 290 just behind.
-- 750mm@F5 is far more forgiving but the best to worst in matching is still 178 ,290, 174. 

Am I following the correct logic? Because that looks to me that the cheapest camera the ASI178 is the best one for short sub DSO on a fast Newtonian. That's not what ZWO recommend.

Surely I'm doing something stupid here?

But the 178 does have the bonus that it's a decent camera for shooting the sun and moon too...!

The two wild cards:
-- The Atik Infinity also seem to have a good sensor size and pixel scale match for the 750mm focal length f5 but but less so on the 600mm f4 where it tends to undersample.
-- Starlight Xpress Lodestar or Ultrastar has a better software experience that outweighs lower specs and greater suitability towards the faster optics of the hyperstar. 

On the 8" f4 you use, Martin, according to the pixel scale CCD suitability calculator, good and exceptional seeing will cause significant undersampling on the lodestar and ultrastar. Do you find that to be an issue, or do you use a Barlow/something else?

In conclusion, unless I'm missing something, my choices are:
-- ASI178 if I'm keeping budget down
-- ASI1600 if I'm feeling flush
-- Lodestar/Ultrastar for software experience and ease of use
-- Atik Infinity to get a bigger sensor while keeping good software experience

One more thing... the A7S sensor is a much better performer at short exposure than any of these sensors. Is anyone doing short exposure stacking with the A7s? I've seen 30s stacks but I couldn't find anything less than that... Or is an equivalent sensor to be found anywhere in an Astro camera?

And thanks again to everyone who is being so helpful here!

[Martin Meredith]

Hi David

A few quick answers:

I believe many use SharpCap with the ZWO cameras. I've only ever used StarlightLive but lots of people judge it to be the easiest and yet in some ways the most powerful too. The ZWO menagerie is not one I've ever tried to get my head around. But I think that the 290 has a lot of fans, as does the 224. I recall a thread some months ago on CN saying why the 178 is not such a great choice, but I can't lay my hands on it at the moment. Maybe it was this one. Still, best to get opinions from owners!

For me, purely based on the images I've seen posted, I find the Infinity a little 'soft' and with a colour cast. Almost certainly these things can/will be 'fixed' in software in the future if that's what users want. Check this thread.

I don't feel undersampled with my 8" f4 setup. But I'm at 2.11"/pixel so I don't really regard that as likely to be significantly undersampled. Seeing is never great around here but I find it adequate on most nights. The route of using a Barlow is a possibility but it does inevitably slow down the system a lot.

cheers

Martin

[HiloDon]

On 2/28/2017 at 13:53, London_David said:

@HiloDon

Hahahah. Okay. 6" SCT. And here I thought I'd settled on a Newtonian!

This sent me off another research dive. Great to have the different angle on this.

So the thing that made me dismiss an SCT originally was star smudging I'd seen in some photos. Your images are spectacular however.  So it seems smudging is entirely fixable with a coma corrector or hyperstar. 

But that 6" is heavier than I was looking at. I know this is kind of crazy thing to be a deciding factor... but my storage space is will fit a 4kg tube but probably not a 7kg one. Does the mount come off, not just the tripod but? The bigger fixed mount would be an issue.

I originally measured my space for a 5" sct which would fit. 6" I think may be too much. I'll double check the physical space again. F1.9 @ 6" would be pretty cool. But since I don't live alone, there are other considerations.

So... I think it's down to the Skywatcher 150pds, or a carbon fiber TS or ZWO at f4. 

Thanks for the camera info too -- I'm starting to get a sense of things now!

I came across a post of yours on Cloudy Nights mentioning that you thought the Ultrastar was best suited for very fast optics. That pushes me away from the SX cameras a little. Possibly towards the Atik Infinity or ZWO. Which sent me on a long dive into cmos territory. Which is my next post...

Hi David,

The C6 OTA comes off the Evo mount.  It has a dovetail connection.  That's another advantage to the Evo.  You can use other scopes on it.  The C6 OTA weighs about 4.5kg.  All Celestron C6's are Hyperstar compatible, so you don't need to get the Evo.  You can use the C6 on other mounts if you want.

I usually don't recommend the Ultrastar unless you have dark skies and faster optics.  It's not very forgiving in LP, especially the color.  The Lodestars have always performed well for me in all types of seeing.  Nytecam has shown what can be done with it in the LP skies of London.