Cheap and cheerful ST80 for NB imaging - any good?

[Gina]

I know I can try this myself when I get a clear night but really wondered if anyone had tried it and what results they got.

I have an ultimate plan to buy three Esprit 80ED scopes and three Atik 460EX cameras to make a pretty super triple imaging rig for DSO imaging in NB.  But until I have the funds I have to make do with a lesser setup.  Currently I have two 460EX cameras and just the one Esprit scope.  (Also, two Evostar 80EDs and one 314L+ camera.)

Now the ST80 has the same focal length as the Esprit. so would match it for FOV.  Chromatic aberration wouldn't be an issue with NB filters of 5nm, 3nm and 5nm for Ha, OIII and SII.  And the image sensor is relatively small so I'm not looking for the large flat image the Esprit is capable of.

I'm just wondering if it would be worth constructing a setup with Esprit 80ED for Ha and ST80 for OIII - both using a 460EX mono CCD camera - for a dual imaging rig.  Or would I be wasting my time?  I do have an ST80 that I used for guiding in the past and is now just gathering dust.

[Alien 13]

Hi Gina

I am not sure but i would think that the differences between a cheap achro and a well designed ED are more than just CA the focus precision i.e pinpoint star shapes even in NB might still cause issues plus the focusser mechanism itself would not be the best.

Alan

[Gina]

Hi Gina

I am not sure but i would think that the differences between a cheap achro and a well designed ED are more than just CA the focus precision i.e pinpoint star shapes even in NB might still cause issues plus the focusser mechanism itself would not be the best.

Alan

That's what I thought but OTOH I have seen some half decent images taken with an ST80.

[Alien 13]

I agree that you can get decent images and have seen a few posted on SGL but if i compare some of my pictures taken with my scope vs a camera lens and view them as a single component of the captured RGB then I can see a difference in sharpness but I would certainly give it a go.

If it works it could be a very cost effective way of building a tripple shooter.

Alan

[Earl]

id saay you can get away with not having a well corected scope but it still needs to be good and have a flatfield to match your ccd. and a good focuser

[Dave In Vermont]

I'd very much like to see some side-by-side images taken with both the ST80 and Esprit 80ED - using identical filters, etc. That would be very revealing - in place of conjecture.

Clear Skies,

Dave

[Gina]

Well, the focuser is actually quite good - it's a rack and pinion and quite smooth.  OK so it's only single speed but that's no problem when adding a stepper motor drive  

I think I'll give it a try   I have the whole big rig indoors ATM so can drill holes for both Evostar and ST.  Without a FR/FF the ST is easier to set up.  The Evostar would need the FR/FF to get the shorter FL.

I might be able to overcome the ST deficiencies by using it for the colour side only, using the Ha from the Esprit as luminance.

[Gina]

I'd very much like to see some side-by-side images taken with both the ST80 and Esprit 80ED - using identical filters, etc. That would be very revealing - in place of conjecture.

Clear Skies,

Dave

Yes, so would I   Unfortunately I don't have a pair of identical filters

[Sp@ce_d]

Hmm I've not used mine for a couple of years.. There's a thought. I'd be inclined to try Ha first though & use OIII on a well corrected scope to avoid any bloat.

Sent from my iPhone using Tapatalk

[laser_jock99]

I tried this with a 6" F5 Bresser achromat a few years back. I worked and it didn't work.......the Ha got through okay but the general quality of the (presumably cheaper) optics was a let down. Maybe if a had a suitable field flattener it would have been better but I suspect not.

Quality optics always come at a price. With a doublet achromat there are four curved optical surfaces that need to be top notch. This is where mirror scopes win out- only two surfaces and one of those is flat!

[RikM]

Here is a bit of the Pelican with an SXV-H9 and Baader 7nm Ha filter on an ST80. I haven't tried OIII or SII on it yet. I suspect the SII should be okay but the OIII may be poor. With tighter filter bandpasses it would be better but still not great. But then the scope cost £100 New and I paid £40 for this one s/h. I have had a fiddle with the focuser which has helped with collimation and function.

[Gina]

That looks pretty good to me

[Gina]

I'm going to provide mounting and electronic focussing for my ST80 I have decided, and see how it performs.

[Thalestris24]

Hi Gina

If you haven't done already, it's worth doing Dion's ST80 mods and tweaks. I've done the focuser bit and tried to 'collimate' as best as I can but haven't (yet!) bothered with flocking.

Finer focusing would be good but maybe your electronic focussing will do very nicely!

https://www.youtube.com/watch?v=Ylb7xnc_03U

Louise

[Gina]

Thank you Louise   Funnily enough, I've just been watching that video - very interesting

[Robp]

I'm interested to see how you get on with this Gina.

The ST80 can be purchased relatively cheaply and I could dual mount it on my HEQ5 with my 130P-DS

[ollypenrice]

One issue will indeed be field curvature. This will be greater in the ST. I doubt that the stars will overlap each other across the whole image when you try to combine them but if you use Registar it will sort that out. Pix might do so as well but I don't use that part of PI.

Olly