Another "help me spend my money" thread

[The Lazy Astronomer]

UPDATE: potential scope options listed a few posts down - any advice much appreciated!

 

Sorry, bit of a long post, but I'd appreciate some advice from you lovely people!

Right, having steered myself away from the idea of a large newtonian, I'm now thinking of going the opposite direction! I've instead come back around to my original desire use a dual scope setup to speed up my data collection.

Now, I see the best option imaging wise to be to take 2 identical (or near identical) scopes and pair with the same cameras, but here are the potential issues I've thought about:

 1. I think my mount would likely not be up to the job of reliably carrying 2x Esprit 100s (quite possibly the heaviest 100mm scope on the planet!!).

2. I like to set up with the minimum of hassle (and trips in and out to the garden) - as such, I leave all my gear fully assembled and carry it out in one go. All in, it weighs about 45kg, I find this heavy, but manageable.

3. I don't have a permanent setup, and with above in mind, I don't think I'd be able to safely move the whole lot due to the extra weight (probably another 15 - 20kg, including additional counterweights), meaning I'd need to move mount and scopes separately, with the added potential hassle of accurately aligning both scopes FOVs each time.

4. A substantial outlay of £4k - £5k, with potentially another £2k - £3k if the mount isn't up to the job (not really affordable, if I'm being honest).

With all of the above in mind, I've come to the conclusion running 2 identical scopes is probably not feasible for me right now.

So, what about a dual scope setup pairing my current Esprit with something much smaller? Obviously this would result in a lower resolution image from the small scope (other factors affecting real obtainable resolution aside), but the thought process in my head was use the small scope with a OSC for colour data, and dedicate the larger scope to hammering out the luminance subs for detail. I think something with around half the focal length, like the the Sharpstar 60 EDPH II would work relatively easily - I'd aim to use roughly the same size sensor in both, so I'd expect it to be fairly straightforward to roughly align their FOVs.

This shouldn't add too much extra weight, so I should be able to continue to move the complete setup in one go, plus significantly less monetary outlay

Does this sound sensible? Anyone with any experience running mismatched dual scopes have some advice? 

The main disadvantage I can think of is it won't really help with narrowband imaging as the smaller scope would potentially not get achieve the same resolution - are any other complications or potential downsides I've not thought of? 

Thanks!

 

Edited January 15, 2023 by The Lazy Astronomer

[Elp]

The only way I have managed to get perfect or near enough FOV match is to setup two separate rigs at the same time (ie on their own mounts and tripods). 

I did manage with two cameras on the same rig, but one was a long lens with a large sensor, the other a smaller lens and smaller sensor, so I could crop the target to the latter. With identical lenses and cameras side by side, your FOVs don't match up, for me it's easier to setup two on similar mounts so they both point dead centre.

It becomes more problematic setting up two side by side when shooting narrowband and the target doesn't emit much signal in a particular bandpass, it's difficult to determine where the second lens is pointing.

Edited January 10, 2023 by Elp

[The Lazy Astronomer]

1 hour ago, Elp said:

The only way I have managed to get perfect or near enough FOV match is to setup two separate rigs at the same time 

Yeah, one of my concerns was matching FOV, but with similar sized sensors, the shorter FL scope FOV would be 3 - 4x that of the longer one - I'm hoping that'll make it easy enough to line up the longer FL FOV to be somewhere within the shorter ones, but would like to get some opinions in case my thinking is misplaced or I've not thought of something. 

[tooth_dr]

I’ve used data from an ED80 to colour the luminance from a 250px.  Same idea as you - high quality lum and ‘adequate’ colour. There was plenty of extra FOV with the colour making it easy to align and plenty to spare to crop the 500mm focal length to the 1200mm.  I did the alignment using diy mods to the dovetail and some shims. It worked fine in providing sufficient resolution for the luminance.  What you are proposing should be ok with the SS60.

Issues: you might get flexure between the scopes, giving eggs stars in one scope.  Probably correctable by BXT but a rigid connection is something to think about to try to prevent it.

I now have two identical scopes and sensors - with the rotatable focuser and an adjustable saddle I can get them very accurately aligned on the same mount.  But in my opinion this setup is only feasible as a permanent setup.  You don’t want to be fine tuning the alignment every time you use it, and it’s too heavy to lift assembled.  I don’t know how heavy the esprit is but I have an APM 105mm and it is definitely on the heavy side at 10kg 😳

 

[The Lazy Astronomer]

Thanks very much @tooth_dr, that's much appreciated.

12 hours ago, tooth_dr said:

APM 105mm and it is definitely on the heavy side at 10kg 

 

Wow ok, I thought the Esprit was heavy at 7-ish kg, but maybe not so much!

[The Lazy Astronomer]

So, I'm going back and forth over potential scope options, I think I've narrowed it down to these potentials:

- Sharpstar 61 EDPH II

- Askar FRA 300

- Askar 65 PHQ

- William Optics Redcat 51

- William Optics GT71

All would be used with any required reducers/flatteners to get a flat field and a FL somewhere around 300mm and I'd most likely use a 4/3 sensor.

I think the Redcat would be the easiest option, plus it's super lightweight, but I worry it might be a bit short, focal length wise, to use to colour lum data from the Esprit.

I don't want the potential to degrade the quality of my images, so I'd like colour correction to be on a par with the Esprit 100 - most of those options listed above have spot diagrams and such available, but l don't really know what I'm looking at if truth be told... Any thoughts anyone? 

[Elp]

Can't really comment on those as I don't have experience, I believe the askar phq and Redcat already have in built optics to negate the need for flatteners, this may also limit your ability to utilise a reducer of your choice.

My widefield is a WO Z61 and I find it performs admirably at anything Ive tried with it be it white light/ha solar, lunar, planetary (tiny planets), and deep sky. I don't think I'd ever replace it as I find it so good so assume some of their other fpl53 synthetic fluorite glass scopes are just as good. I tried imaging Thor's Helmet a few weeks back, a very small target and still got a decent result of it at 370mm focal length, I've also got a reducer which allows 234mm focal length at f3.9, versatility is another bonus with this type of setup.

[Guest]

If you are wanting to spend the big bucks, i would give Stellarvue a look.  They will be glad to take your money and give you one hell of a good scope in return