Scope and mount for 5x3 shed obsy

[Chris]

I'm putting together a small 5x3 foot shed/osby on the garden patio so I can more conveniently observe, take quick snaps (EAA), and hopefully at some point get back to doing a bit of actual science with a scope.

My criteria is:

- 8" or above aperture

-Goto

&

-Fit's the 5x3 space for storage (Will be carted out several feet when being used)

-Budget = £700 plus or minus a bit.

I've just started to advertise for an 8" SCT e.g. LX90 as it fits the budget, but before I commit to finding a classic fork mounted SCT I was wondering if I'm missing a trick?

I want to be as sensible as possible and would love to put a stop to my chopping and changing of kit, basically I would like to get it right.

With this in mind, are there any other alternative setups which both fit the criteria and 5x3 footprint?

 

 

 

 

 

 

[Chris]

Let me make this a bit more interesting, we all like fantasy spending right!?  If you had £700-800 to spend on a complete setup with semi decent aperture to fit limited space, where would you put your money and why? second hand or new.

[Louis D]

Would the walls drop down?  That might be sufficient space to store a pier mounted scope in, but I don't see how you could move around it if the walls didn't drop flat to the ground.  If it's on a tripod, you'll definitely trip on the spread legs of it in the dark because they'll be spread about 3' or more across.

[Chris]

1 hour ago, Louis D said:

Would the walls drop down?  That might be sufficient space to store a pier mounted scope in, but I don't see how you could move around it if the walls didn't drop flat to the ground.  If it's on a tripod, you'll definitely trip on the spread legs of it in the dark because they'll be spread about 3' or more across.

Hi, the shed has double doors at the front so a suitable scope can be carted out onto the patio. I didn't make this clear so I've amended my first post.

I'm just looking at various scope/mount options which will fit the space for storage, and will easily be wheeled out and setup for use. A fork mountet SCT probably is the best option but just wanted to call on the collective to make sure I wasn't missing a trick

[Louis D]

You could always go with a larger truss dob on wheels.  Given a tall enough shed, you could leave it assembled and just wheel it out intact as another option.  There are multiple ways to make this approach work such as wheelie bars or a simple cart with wheels.

[Chris]

I really want to explore all options to get it right so thanks  

I've just checked and the shed doors are 73" / 6' 1" tall, this seems plenty but I can check this against particular scopes. I'm open to ideas other than my original one of a fork mounted SCT, if I choose a Dob it would need to be a goto Dob though because I tend to dabble with basic imaging/EAA as well as visual, plus I fancy playing with Spectroscopy and Photometry at some point.

This goto Dob is in budget:

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-200p-flextube-goto.html

and this one wouldn't be out of reach if I continue to save my pennies.

https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-250px-flextube-goto.html

The goto Dob's do look sensible if they track well? The only other down side I can think of is that I would lose 10 degrees of sky or so compared to a tripod mounted scope as my views are obstructed by a garage and trees.

 I do still have an Helios 200p f/5 OTA, so could just buy a goto mount for that if it would all fit in the 5'x3'.

Would be really good to discuss compare the merits and issues of the following:

1) Fork mounted SCT like an 8" LX90/LX200

2) Goto Dobsonian 8" or 10"

3) Buying a goto mount for my existing 200p f/5

Any input on the above scopes for my little pull out obsy would be great. My heart wants a fork mounted SCT but my brain isn't entirely sure!.  

Which way would you guys go in my shoes, honestly? 

 

[Louis D]

SCTs lend themselves very well to astrophotography; Dobs, not so much.  What 8" SCTs have you been looking at?  They get pretty pricey pretty quickly.  A goto mount capable of holding that 200p OTA for astrophotography will be pretty pricey as well (possibly a SW EQ6).

I wouldn't worry about that last 10 degrees as it's usually pretty distorted by atmospheric effects and haze.  The only things you're likely to be looking for there will be comets, Venus, and Mercury (objects close to the sun at sunrise/sunset).  For DSOs, you're better off waiting for them to rise higher or traveling south.

[iapa]

I have had it pointed out to me that an 8" SCT with focal length 2000mm is likely less simple to use for DSO imaging due to the fact that is has a very tight field of view so object move quite a bit relatively in it's field of views which means a VERY good mount would be needed. Thanks to Olly amongst others for that feedback. 

excellent for planetary tho I have been told.

[Louis D]

3 minutes ago, iapa said:

I have had it pointed out to me that an 8" SCT with focal length 2000mm is likely less simple to use for DSO imaging due to the fact that is has a very tight field of view so object move quite a bit relatively in it's field of views which means a VERY good mount would be needed. Thanks to Olly amongst others for that feedback. 

excellent for planetary tho I have been told.

I have generally found that small obstruction Newts and unobstructed refractors of equal aperture do better than SCTs on planets because of their large central obstruction.  That large obstruction tends to decrease contrast by throwing more image energy into the outer diffraction rings.  Contrast is very important in planetary viewing.  Of course, the Newt and the refractor will generally be longer instruments than the SCT and will thus require a sturdier mount for astrophotography than the SCT would.  It's all about trade-offs.

[Chris]

These are the kinds of discussions I like to have when brain storming new kit  I look forward to joining in once the kiddies have stopped climbing all over me and are put to bed!

[Chris]

On 9/19/2016 at 02:35, Louis D said:

SCTs lend themselves very well to astrophotography; Dobs, not so much.  What 8" SCTs have you been looking at? 

I think there might be a USA vs UK divide when it comes to thoughts on SCT's for DSO imaging? This might sound contraversial, but over the years my observation is that folks tend to opt for ED/Apo refactors or fast Newts in the UK, then I hear how popular SCT's are for DSO imaging on CN, Youtube etc.

 I quite like how flexible and compact per aperture SCT's are. You can reduce the standard f10 down to f/6.3 for medium format imaging, f/3.3 for small chip EAA, and given the right SCT f2 for the brave! Barlowed SCT's are of course also great for planetary imaging. As a reflector they seem like a good choice for Photometry and Spectroscopy too as they bring all wavelengths of light to the same focus.   

Downsides seem to be focal length which puts more demand on tracking accuracy and mirror flop....Oh and dewing of the corrector.

As for Dobs and imaging, I wouldn't do long exposure DSO imaging with one but I do wonder if the Goto Dob's can handle the short exposure imaging that the latest CMOS sensors seem to allow, and also EAA?

SCT wise, I've been looking at the idea of getting a Classic Meade LX90/200 due to my current budget of aroud £700, but this might be Russian roulette with the electronics getting on in age. The other Option is to get something like a C8 XLT and stick it on a newer GEM/AZ goto mount but I don't have enough on the piggy bank with this yet. Thirdly, I could put all my money into a mount, use my Newt for now and get a C8 later down the line.   

On 9/19/2016 at 02:35, Louis D said:

  A goto mount capable of holding that 200p OTA for astrophotography will be pretty pricey as well (possibly a SW EQ6).

Agreed if your into long exposure AP. Not my thing now days, mainly do visual with a bit of smash and grab imaging here and there  With this in mind I can probably get away with a lighter mount, the CG5 I had for it held it very solidly. Probably would have kept it if it had Goto!

 

On 9/19/2016 at 02:35, Louis D said:

I wouldn't worry about that last 10 degrees as it's usually pretty distorted by atmospheric effects and haze.  The only things you're likely to be looking for there will be comets, Venus, and Mercury (objects close to the sun at sunrise/sunset).  For DSOs, you're better off waiting for them to rise higher or traveling south.

 My bad, I probably should have mentioned my limited horizon. There is a small ish gap to the south before the neighbours pitched roof garage kicks in blocking upto about 35 degrees. West is the tall tree woodland at the bottom of the garden, I estimate blocking upto 50-55 degrees, North isn't too bad about 25 degrees blocked, and East is our 3 story house so pretty much 90 degrees blocked. 

I think this is possibly one of the only downsides to the Goto Dob idea, with a tripod mounted scope I can get better angle at the sky. It's all pro's and con's though which I need to weigh up!

 

[Chris]

2 hours ago, iapa said:

I have had it pointed out to me that an 8" SCT with focal length 2000mm is likely less simple to use for DSO imaging due to the fact that is has a very tight field of view so object move quite a bit relatively in it's field of views which means a VERY good mount would be needed. Thanks to Olly amongst others for that feedback. 

excellent for planetary tho I have been told.

Yes, got to agree that if you want to do long exposure imaging, a native 2000mm scope will be a challenge compared to a 500mm frac and place much more demand on the mount in terms of tracking accuracy.

The analogy I like to use is a short focal length scope is like holding your finger out in front of you and keeping it still, whist the long focal length scope is more like holding a pool cue out in front of you and keeping the end of the cue still! We can all see which would be easiest.

On the plus you can reduce SCT's down in various weird and wonderful combinations. Before I moved house and waved god bye to my first obsy, I had a C8 Edge plus .7 reducer on an NEQ6. I did dabble with DSO imaging with it and I'm sure it would have been excellent for PN's and most galaxies if it wasn't for the fact that I had the worst of the worst EQ6 which was so badI sold it for absolute peanuts.

I definately had my best ever views of planets with my C8 Edge! I no longer have that kind of budget now days so beggers can't be choosers

 

[Chris]

2 hours ago, Louis D said:

I have generally found that small obstruction Newts and unobstructed refractors of equal aperture do better than SCTs on planets because of their large central obstruction.  That large obstruction tends to decrease contrast by throwing more image energy into the outer diffraction rings.  Contrast is very important in planetary viewing.  Of course, the Newt and the refractor will generally be longer instruments than the SCT and will thus require a sturdier mount for astrophotography than the SCT would.  It's all about trade-offs.

I've never owned a long focal length small obstruction Newt but have heard good things as dedicated planetary and double star scopes. I'm personally not keen on diffraction spikes on planets but then again you get lots for your money with a Newt.

As for mounts and AP, wouldn't it be more focal length than physical length that dictates how accurate/sturdy a mount needs to be? Other than catching the wind of course  It's nowt to do with the thread but then again it's my thread so when in doubt check with @ollypenrice

[Louis D]

The latest crop of corrected SCTs seem to produce a much sharper image than the SCTs of 20 years ago.  High end newts then and now seem equivalent.  There didn't seem to be any high end (optically) SCTs back then.  APO refractors also seem somewhat improved over the last 20 years.  Perhaps better glass and optical prescriptions?

I can't say that I've ever noticed spikes on planets in Newts, just bright stars.  There is light spillage around planets due to the diffraction.  I have noticed less contrast and sharpness on planets in the best Newts than in the best refractors.  However, moving up to a 12 or 15 inch Newt with a premium mirror and mid f-ratio demolishes a 4 to 6 inch APO refractor or 8 inch SCT due to vastly increased resolution and image scale (at least here in Texas with our fairly good seeing).  I chose those for comparison because they can all be had new or possibly used in a similar price range.  The big Newts in a dob mount can be used for imaging with a decent equatorial platform and shorter exposures.  However, adding a filter wheel to the imaging train can be difficult due to limited back focus.  That's where the SCT or refractor shines.  Both can produce lots of back focus with ease.

[RobertI]

Hi Chris, an interesting conundrum! I think you've outlined some very good reasons for getting an SCT and also if you are carting it in and out then an SCT is more portable than a newtonian. Also sounds like a good goto AZ mount would meet your needs for short exposure imaging, small footprint, luggability (no counterweights) and ease of setup. So how about a used Nexstar 8SE? I believe you have some experience of these mounts so you are probably well placed to comment on this. Also the underrated and free Nexremote software (basically a Software only version of the handset) would allow you to remote control the scope in case you wanted to do your EEA from indoors.  

[ollypenrice]

10 hours ago, Chris Lock said:

 

As for mounts and AP, wouldn't it be more focal length than physical length that dictates how accurate/sturdy a mount needs to be? Other than catching the wind of course  It's nowt to do with the thread but then again it's my thread so when in doubt check with @ollypenrice

Yes, this is correct. In fact what really defines the tracking accuracy needed by a partiular scope-camera pairing is the pixel scale in arcsecnds per pixel. The fewer arcsecs per pixel you are catching the better your accuracy needs to be. For a given camera this does means more FL needs more accuracy.

One issue with SCTs for deep sky imaging is that that they can only reach a sensible pixel scale on cameras with large pixels or cameras which can be binned 2X2 or even 3X3. If the pixel scale is too small its resolution will be blurred out by the seeing and the guiding error so all you get for your long focal length is a smaller field of view, which is a bit pointless since you can crop a widefield image. You will not get more detail because it will be consumed by seeing and guiding error.

Olly

[iapa]

RE. Olly's point around pixel scale, after he mentioned this in his reply to my post in an earlier thread just after I got the C8, I did some numbers in a spread sheet the other day out of curiosity; based on the gear I have as I had seen somewhere (I will look it up later) that the pixels scale ratio between the guiding and imaging should be less than 4.

So, C8 2032mm fl OTA, ST-80 400mm fl frac as guide scope and touptek mono guide cam (3/75um pixels, 1280 x 96 which is similar to other guide cams).

To achieve that, turned out that the imaging camera would need to be in the order of 8um pixel size unbinned. I didn't look too much at specific models - the QHY 9 I think is in that area, and also c£1K too

Of course the AVX also probably just the wrong side of useful for accuracy. The CGEM-DX may just wing it - in a clear, still, windless days.

That of course gets us away from the OPs requirement to fit in a 5' x 3' shed due lack of maenuverabilty of it.

As an aside, when I upgraded from a 130mm reflector to the 200P-DS on the AVX, it was pushing 80%+ of the AVX maximum load. I've read that 50-70% is about where you should aim to be - hence the CGEM-DX.

Having said that, managed a couple of unguided 30s exposures of M27 with the 200P-DS on the AVX with a Canon 70D. Yes, some star trails, yes not quite focused, but in my somewhat biased view, good enough that I thought there was potential if I could get a decent number of guided subs to stack.

1st light , C8 unguided on the AVX got me separation and colours of Albireo it was quite windy that night.

So, in my view, AVX is manoeuvrable with C8, ST-80 all setup. Should fit in 5' x 3'. I'd suggest an 8" reflector would need to be removed and added as needed - that bulk makes it a bit more harder to move the whole rig.

Other similar sized mounts are available , I just happen to have Celestron's.

 

[Chris]

5 hours ago, RobertI said:

Hi Chris, an interesting conundrum! I think you've outlined some very good reasons for getting an SCT and also if you are carting it in and out then an SCT is more portable than a newtonian. Also sounds like a good goto AZ mount would meet your needs for short exposure imaging, small footprint, luggability (no counterweights) and ease of setup. So how about a used Nexstar 8SE? I believe you have some experience of these mounts so you are probably well placed to comment on this. Also the underrated and free Nexremote software (basically a Software only version of the handset) would allow you to remote control the scope in case you wanted to do your EEA from indoors.  

Hi Rob, how are you? yes for my needs the SCT does seem like a good fit, and for visual the coma and big stars can to some extent be negated by the .63 reducer. I didn't include the 8SE as I've heard lots about the C8 being too much for the SE mount, and just looking at it I can see why. Shame as second hand it would be the right price bracket. I never even thought about the Nexremote software, that could be interesting if I get a Celestron, and I do really like Celestron products as a whole

Ona side note, had a chance to play with the Tal yet? 

[Chris]

9 hours ago, Louis D said:

The latest crop of corrected SCTs seem to produce a much sharper image than the SCTs of 20 years ago.  High end newts then and now seem equivalent.  There didn't seem to be any high end (optically) SCTs back then.  APO refractors also seem somewhat improved over the last 20 years.  Perhaps better glass and optical prescriptions?

I can't say that I've ever noticed spikes on planets in Newts, just bright stars.  There is light spillage around planets due to the diffraction.  I have noticed less contrast and sharpness on planets in the best Newts than in the best refractors.  However, moving up to a 12 or 15 inch Newt with a premium mirror and mid f-ratio demolishes a 4 to 6 inch APO refractor or 8 inch SCT due to vastly increased resolution and image scale (at least here in Texas with our fairly good seeing).  I chose those for comparison because they can all be had new or possibly used in a similar price range.  The big Newts in a dob mount can be used for imaging with a decent equatorial platform and shorter exposures.  However, adding a filter wheel to the imaging train can be difficult due to limited back focus.  That's where the SCT or refractor shines.  Both can produce lots of back focus with ease.

Yeah definately the Edge C8 was almost like using a big frac in terms of sharpness,.... almost. My C8 xlt before it had coma and biggr stars but I've heard from a number of sources that the .63 reducer really helps with this. This might be worth a try as not got the budget for Edge C8's anymore.

Spikes on planets I have noticed with Newts, not bright spikes like on stars but they were there in the form of faint wide spikes. I've only ever used cheap Synta Newts though. The fact that they are so much cheaper does outweigh this issue if I'm being sensible

The back focus on SCT's and fracs is very very handy

[Chris]

4 hours ago, ollypenrice said:

Yes, this is correct. In fact what really defines the tracking accuracy needed by a partiular scope-camera pairing is the pixel scale in arcsecnds per pixel. The fewer arcsecs per pixel you are catching the better your accuracy needs to be. For a given camera this does means more FL needs more accuracy.

One issue with SCTs for deep sky imaging is that that they can only reach a sensible pixel scale on cameras with large pixels or cameras which can be binned 2X2 or even 3X3. If the pixel scale is too small its resolution will be blurred out by the seeing and the guiding error so all you get for your long focal length is a smaller field of view, which is a bit pointless since you can crop a widefield image. You will not get more detail because it will be consumed by seeing and guiding error.

Olly

Ah yes, that's other thing , this is why I used a Canon 350D for my Edge C8 with .7 reducer. This gave me 1"/pixel. If my EQ6 wasn't such a nail (massive PE from the worm gear) I would have carried on trying with this combo a bit longer I reckon. The Edge really does have a flat field and mirror locks that work!

[Chris]

1 hour ago, iapa said:

 

So, in my view, AVX is manoeuvrable with C8, ST-80 all setup. Should fit in 5' x 3'. I'd suggest an 8" reflector would need to be removed and added as needed - that bulk makes it a bit more harder to move the whole rig.

Other similar sized mounts are available , I just happen to have Celestron's.

 

 

 I think that kind of setup would both fit and be manageable so it's definitely on the table. If I had to just buy the mount due to budget and use my 200p I could store the OTA next to the mount in the mini shed if it fit's. The C8 would be a better fit if budget allows. An AZ goto would be an easier setup process, but the cheaper single arm ones don't tend to have a good payload, hmmm what to do?

I need to find even more things to sell 

 

[RobertI]

6 hours ago, Chris Lock said:

Ona side note, had a chance to play with the Tal yet? 

Hi Chris, I have had the Tal out very briefly on my balcony for 20 minutes. The conditions were really too poor to make an assessment, I just wanted to play with my new toy!  It's a lovely thing and I am looking forward to some double star action with it. The Tal sits mid way between my 72mm F6 frac and my C8, so once I have had a couple of sessions, I am planning to do a side by side comparison of some doubles between the three scopes at similar magnification. Should be interesting. I'm loving it so far!

Sorry to divert the thread.....  

[Chris]

Thanks Rob, hope you get good conditions soon  All I'll say is sharp and flat, let me know if you agree

Oh and don't be sorry, I asked so I'm the thread diverter 

[RobertI]

4 minutes ago, Chris Lock said:

Thanks Rob, hope you get good conditions soon  All I'll say is sharp and flat, let me know if you agree

Oh and don't be sorry, I asked so I'm the thread diverter 

I certainly will.