nfotis

11 hours ago, PeterC65 said:

Thanks @vlaiv, that makes more sense.

So the two formulae apply to different situations, the F number formula for very short exposures and the FL formula for longer exposures.

I take your point that the required resolution (arcseconds per pixel) depends on more than just the seeing conditions, also on the mount guiding and the performance of the scope, but it sounds like the formula used by Astronomy Tools is correct and useful when considering longer exposures, just that taking account of only seeing conditions is not the whole story.

My takeaway from this is that when imaging planets I should be using the Mak, or the refractor with a Barlow. From trial and error, I actually use the refractor with a x2.25 Barlow giving me F13.5, close to what the F number formula is saying (2.9um x 4 = F11.6).

 

In short, planetary imaging (or "lucky imaging") is quite different from DSO imaging.

A rule of thumb for planetary imaging says you want f-ratio 4x to 5x the pixel pitch. So, with a 3nm pixel, you want f/12 to f/15 or so, with a 4nm pixel you want f/16 to f/20.

Hope this helps,

N.F.

And here's another approach in modifying the Skymax 180:

Personally, I think that I would use an external focuser instead, as the newer copies have an SCT-compatible visual back.

N.F.

To the OP:

You may be interested in viewing this video, where the guy modded his Skymax 180, with flocking, rings and rails etc.

Personally, I watched it at 2x speed and using subtitles because it was a bit slow-moving, but it was quite interesting.

Cheers,

N.F.

I doubt that Skywatcher don't know what they are doing. I own the Skymax 180, even used it with an old HEQ5 mount with the small saddle. No problems so far.

If you want to load it heavily with accessories, a larger saddle should help. There's also the option to add tube rings etc, if you feel it necessary.

Celestron offers a version with a wide (Losmandy compatible) dovetail, but it's not easy to locate in Europe (and it's costly)

N.F.

Note that the ASI462 has been superseded by the ASI662. The newer sensor looks quite improved, if I remember correctly.

N.F.

7 hours ago, Ratlet said:

Looks like my favourite cut price astronomy maker is bringing out a camera of their own with this sensor:

https://www.svbony.com/blog/one-of-the-new-products--sv705cc-eaa-/

Itll be interesting to see how it compares.

Quite intriguing, indeed. I wonder  what's the expected pricing, too.

And I see that they're going to introduce a mono sensor, too.

N.F.

For planetary, I think that a Skymax 180 or a C9.25 are great tools.

If you want also a GEM mount, a HEQ5 can carry both for visual/planetary (the 7" Mak is easier on the mount, but the C9.25 offers more aperture).

An electronic focuser is very helpful for good focus without too much vibration from your fingers.

N.F.

My understanding is that the minimum mount for imaging and go-to operation would be a HEQ5 or similar.

This puts a bottom limit of 990 UKP to your budget (maybe buy used? I bought mine for 550 EUR here in Athens).

Add a 80ED refractor, and this reaches 1.600+ UKP if you go for the Skywatcher 80ED DS-Pro, less if you go for an SVBONY or similar.

The HEQ5 mount can be carried as a set (head and tripod) without the counter-weights (these would need another trip).

N.F.

By the way, I checked at the Orion site and this saddle isn't available anymore (no positive response from the local dealer when I discussed that).

So, it's an ADM or similar (Altair does give an "Out of stock message" for their offerings) I guess...

N.F.

As I own a HEQ5 mount, I can attest to its capability to handle even a C9.25 for visual/planetary.

Touching the tube for refocusing is a hassle, though (too much shaking) - investing into an electronic focuser will make your life much easier.

Also, I own a Skymax 180, which is easier to handle than the Celestron, and quite cheaper.

Another option would be a Classical Cassegrain CC8, if you aren't bothered by spider vanes (it's an open tube system).

All these range between 2350 to 2700mm focal length. The C9.25 can use also a 2x Barlow easily, if you want to image planets (the Skymax 180 is already f/15, so a Barlow might not work well with it)

N.F.

You may want to check this video (I watch it at 2x speed due to their length), where this guy adds lots of stuff on his Skymax 180:

You may want to add into consideration the SVBONY 102ED/7 as well?

These seem quite good to me (I bought mine direct from the company, with reducer/flattener, and I am awaiting for a guide scope etc to complement it)

N.F.

A HEQ5 mount can handle a Skymax 180 (that's a 7" Maksutov), if you can add an electronic focuser.  The view is quite contrasty and sharp. You may need to use a Reflectix dress of the OTA if your local temperatures are swinging too fast, in order to control internal air currents.

At 2700+ mm focal distance, trying to focus manually is a bit irritating (too sensitive to vibrations with the standard tripod). It's quite more manageable than a C9.25 on that mount, weight-wise (yes, I tried one on my HEQ5 mount).

Of course, a C9.25 is an even better tool for shooting planetary, because at f/20 with a 2x Barlow, you get nearly 4700mm focal distance. It requires some more effort, though, with the mount.

N.F.

Note: if you want to view planets and the moon, a Maksutov scope like the Skymax 127 would be a good start.

There's no scope that does everything. Because I live in a heavily light polluted city, I wanted a scope suitable for planets, moon etc., and in this specialty focal distance is a big advantage.

N.F.

Hello, and welcome to SGL.

The typical response could be "Aperture is king, but mount is the queen"

A Dobsonian scope will offer the maximum aperture for a reasonably stable mount in a given budget. And it doesn't need electricity in order to operate (you are moving the scope manually).

A scope like a GSO 8" Dobsonian is a very nice starting scope for observing - around 450 EUR in a European dealer

(note that I don't own a Dobsonian myself, I use a Maksutov and a refractor mostly)

If you want a refractor, an ED doublet like the SVBONY 503 80mm is a nice introduction (and can also be used for astrophotography), but you will need a mount too.

N.F.

On 16/07/2022 at 16:36, Space Hopper said:

Looking at the current crop of these new mounts, one can only assume it won't be too long before the mainstream jump on the bandwagon ?

ie Sky Watcher, Celestron, Vixen ?

Synta are good in making mass production of proven technologies.

After ZWO and other companies pioneer these technologies, the mainstream companies may decide to invest money and effort into modern mounts.

That said, these harmonic drive mounts seem to focus more on portability, not to high accuracy or operation with long focal length scopes like the C11

(if you are going to use a C11, you don't care too much about the weight of an EQ6-R or a G11 mount, I guess...)

N.F.

The nice thing about the HEQ5 is that it's light enough you can carry it assembled in one piece. The EQ6-R is so heavy that it needs to be carried in two pieces (the head alone is 15 kg).

I bought mine used for 550 EUR two years ago. A bit agrarian and it needs some set-up and polar alignment, but it does the job (I have loaded it up to a C9.25 and a Skymax 180 for planetary imaging, without guiding). A bit shaky when touching such large scopes with very long focal distances (a remote focuser is very useful). I haven't used mine with a guiding camera, but it should work well with refractors up to 4-5 inches.

If weight is a major parameter, you may want to check iOptron and their CEM series (eg CEM40). If you need extreme portability, the new generation of strain drive mounts like the ZWO AM5 sound quite promising (but you pay extra for that portability).

Cheers,

N.F.

Interesting thread.

I was always intrigued by Hydrogen-alpha scopes, but the price is a major deterrent.

The Daystar Quark is an intriguing idea, but I am put off the various QA stories which rise quite often.

Lunt and Coronado seem the safe options when speaking about "amateur" H-alpha scopes.

Instead of a Herschel wedge, maybe a Baader Astrosolar film on a Cassegrain scope would be cheaper and easier to work with?

You get a long focal distance and a large aperture together. If all you have is a refractor, a Herschel wedge is probably a sharper solution, though.

For me, an ideal combination could be an SCT or Maksutov with Astrosolar film and a Baader solar continuum filter for white light, and an 102ED refractor for CaK or Hydrogen-alpha observation and photography?

N.F.

2 hours ago, vlaiv said:

I've seen some images of ISS taken with large manual dob.

I was seriously impressed - but I don't think it was manually tracked - but rather - push / capture fly thru, push / capture fly thru and so on multiple times to accumulate enough frames for stacking.

Oh, I think that there's a terminology problem on my part.

When I say "manual tracking" I mean something like these manual Dobsonians did following the ISS (is "manual push" the correct term?)

So, I could/would use an AltAz mount like the Rowan 75 in manual (with a long pole) and shooting with the camera while turning the scope?

Adding a manual tracking system with eg a joystick would be another level of cost/complexity.

N.F.

In my original post, I wrote about the possibility of manual tracking.

Would this be workable?

N.F.

Hello everyone,

in recent days I was playing with tracking airplanes with my Canon 100-400L IS II lens (and a 1.4x extender) on my crop sensor 80D.

The results were OK, but even with an effective 900mm lens (in film terms) these twin jets are quite small in my images shot while flying high.

I was thinking about using my Skymax 180 or my C9.25 as a possible tracking scope for these targets, but my own mount is a HEQ5 Pro GEM, which doesn't seem very suitable for the task.

An idea was to use a manual AltAz mount and try to manually track the overflying airplanes using my Canon or an ASI462 camera (I suspect the latter will be harder to keep the airplane in frame).

I append  a typical view with my Canon lens, and a typical crop I would like to attain with a scope, to give you an idea.

Cheers,

N.F.

Logically, you should receive more details with the larger aperture.

That's, if you can cover the whole eight inches with the Astrosolar film, of course.

N.F.

I feel that with all these new sensors and sizes, the field of view calculator will need an overhaul and get the whole system sensor-centered?

I am having a hard time comparing all these models (see the recent Player One planetary cameras as well)

N.F.

16 hours ago, Ags said:

I'm not a big fan of the views offered by the C6, I think I prefer Maks. I can always pick up a Skymax 127 at some point.

If you can upgrade to the Skymax 150, that would be really nice IMHO.

I started with the 127, and decided to jump directly to the 180

N.F.

Quite different animals.

For planetary photography, focal distance and aperture are king (like a C9.25 or Skymax 180, for example)

If you can stand it financially, keep both the C6 and go for the refractor as a complementary tool.

N.F.