Beginner Astro Photography Rig Idea

[RJC]

Hi,

I'm just exploring a possible entry into some astro photography.

My initial idea is the below for a starter rig.
It would be great to hear from more experienced APs to see if this makes sense.

- Star Adventurer 2i Pro or GTI?
- Some sort of carbon fiber tripod legs
- Evolux 82 ED
- ZWO mini guidescope
- ZWO ASI120mm Mini guide camera
- ZWO ASIair Mini
- ZWO ASI183MC

Any input would be great!

Thanks

[michael.h.f.wilkinson]

I wonder if the star adventurers are solid enough for an 82 mm refractor. I have an APM 80 mm F/6 triplet, usually used with 0.8x focal reducer, and use a more substantial mount (Vixen Great Polaris, although I plan to try out the iOptron HEM15 shortly). I have no experience with the star adventurers, I should add. Just my tuppence

[ollypenrice]

I share Michael's concerns. I tend to think of the star adventurer as a camera lens mount rather than a telescopic one, especially since the tiny pixels of modern cameras make an 80mm scope quite high resolution these days.

There is nothing worse than being under-mounted.

Olly

Edited January 29 by ollypenrice
False click

[Elp]

What do you want to image? The SAGTI is in a different league, it's a proper compact mount, the SA is just a star tracker, though they say and people do mount small refractors onto it, when I had one I was hesitant to mount my 60mm refractor onto it, never mind an 80mm.

[RJC]

Thanks for the advice everyone.
I'd roughly calculated the weight of everything and it should fall within the 6KG payload limit, I know you ideally don't want to get too close to that.

@Elp I would like to image DSOs, not interested in planetary/lunar particularly.
I ideally want to keep the rig as light weight as possible so I can take it on holidays around the UK etc. and also get from my house to some nearby dark sky sites.

I should also point out, I already have the Evolux 82, hence that scope is in the list.

[ollypenrice]

22 hours ago, RJC said:

Thanks for the advice everyone.
I'd roughly calculated the weight of everything and it should fall within the 6KG payload limit, I know you ideally don't want to get too close to that.

@Elp I would like to image DSOs, not interested in planetary/lunar particularly.
I ideally want to keep the rig as light weight as possible so I can take it on holidays around the UK etc. and also get from my house to some nearby dark sky sites.

I should also point out, I already have the Evolux 82, hence that scope is in the list.

Looking at the payload capacity is all very well but it is only half the story. The accuracy of your tracking also needs to support the image scale at which you are imaging. If it doesn't, you might as well image at a shorter focal length and get a wider field of view with no loss of real resolution. This calculator will give image scales. https://www.12dstring.me.uk/fovcalc.php

Whatever your image scale in arcseconds per pixel, your guide error RMS in arcseconds must be no more than half that. A good HEQ5/NEQ6 can manage about 0.5" RMS under guiding but beware, it might be twice that.

Your mount must track accurately enough to support your image scale. How accurate are the small Skywatcher mounts? I've no idea but don't buy one without finding out. Users on here who autoguide will know.

Olly

Edited January 31 by ollypenrice
typo

[Elp]

Not so sure on that calculator. I've imaged with my WO Z61 fine with an azgti in EQ mode. No way does that mount do half of the image pixel scale ratio, it typically guides around 1-1.2 RMS, the best I've got is around 0.6-0.8 with an OAG but that was a one off. The images however come out fine, loss of images due to guiding errors maybe 5-10 percent, but my rig is 6.5Kg so overloaded on it. My hem15 is more reliable in terms of little to no loss of subs.

For the OP, maybe you could adapt an azgti into EQ mode, but if you've got the funds a ZWO AM3 or Ioptron hem15 will be better, the lack of need for counterweights make them more portable, paired with a good carbon fibre tripod and even lighter transportation setup. They'll also be more future proof for larger setups, I've imaged with my C6 and Starfield 102 with the hem fine.

But yes, in general you want a mounts max payload capacity to be a significant percentage higher (think near 25-50 pc more) than your actual, especially for imaging, and for per sub reliability.

Edited January 30 by Elp

[ollypenrice]

40 minutes ago, Elp said:

Not so sure on that calculator. I've imaged with my WO Z61 fine with an azgti in EQ mode. No way does that mount do half of the image pixel scale ratio, it typically guides around 1-1.2 RMS, the best I've got is around 0.6-0.8 with an OAG but that was a one off. The images however come out fine, loss of images due to guiding errors maybe 5-10 percent, but my rig is 6.5Kg so overloaded on it. My hem15 is more reliable in terms of little to no loss of subs.

For the OP, maybe you could adapt an azgti into EQ mode, but if you've got the funds a ZWO AM3 or Ioptron hem15 will be better, the lack of need for counterweights make them more portable, paired with a good carbon fibre tripod and even lighter transportation setup. They'll also be more future proof for larger setups, I've imaged with my C6 and Starfield 102 with the hem fine.

But yes, in general you want a mounts max payload capacity to be a significant percentage higher (think near 25-50 pc more) than your actual, especially for imaging, and for per sub reliability.

We can't argue with the facts, though.  If your RMS is 1-1.2 arcseconds your captured resolution will be about twice that. (This is only a rule of thumb.) That doesn't mean your images won't be good because an image with a resolution of 2 arcsecs can be great. I spent many years using a rig that worked at 3.5 arcsecs per pixel. What it does mean, though, is that you could have a much wider field of view from a shorter focal length and capture with just the same real resolution.

When you reject an image because the stars are elongated you are seeing a difference in the guiding precision of one axis against the other, hence elongation. If your guide errors are equal on both axes you will still get round stars but potential detail is still being blurred out.

This is important for the OP to understand because he might be tempted by a larger, costlier, longer FL scope in search of more resolution when, in fact,  a smaller, cheaper, lighter scope might give the win-win benefits of better stability, no loss of resolution and a wider FOV. A region of interest can also be cropped from the widefield with no loss of detail.

Olly

 

[WolfieGlos]

On 29/01/2024 at 10:37, RJC said:

- Star Adventurer 2i Pro or GTI?
- Some sort of carbon fiber tripod legs
- Evolux 82 ED

I can offer some real world experience here. I used to use the Star Adventurer 2i with the Skywatcher Evostar 72ED, mounted on a carbon fibre tripod. The 72ED was lighter than the Evolux you have listed, and the 2i really struggled at times, even with a guidescope.

It was generally fine for 1 minute subs (GUIDED), but at 2 or 3 minutes I had a scrappage rate (due to stars trailing in the images) of anything between 10-40% depending on accuracy, wind, etc. As soon as I bought a HEQ5, that scrappage rate dropped to zero.

I followed various Youtube reviews/videos where people used this successfully. And whilst I did get success with it, it was more effort than it was worth, and so I would really recommend against getting the 2i with any form of scope. Widefield camera lenses or possibly a Redcat at 250mm maybe.

I haven't used the GTI, but because it has the same capacity as the 2i, I can only imagine it being similar, although DEC guiding might assist.

[Elp]

4 hours ago, ollypenrice said:

If your RMS is 1-1.2 arcseconds your captured resolution will be about twice that.

This may explain why when registering my FWHM tends to be approximately double the value I get when focusing. I don't think about the specifics, I just test and carry on.

Agree on using shorter FL optics, even camera lenses. So much less hassle than larger, heavier scopes.

[RJC]

Thanks All, great advice and insights.
I'll have a think about which direction to go.

[900SL]

All I can add is don't buy a SW SA 2i and expect to get anything but headaches with a refractor.

You'll no doubt hear from some who recommend it, but Lordi only knows why.

It has significant periodic error, wobbles like a top and is only suited for wide angle DSLR imaging at short exposures. Mine was junk. Plus, it's a tracker, so can only guide in RA, which is a waste of time. And trying to find and frame targets will have you pulling your hair out.

Those you tube influencers who promote this clockwork pot metal poor tolerance thingy have no morals.

Instead, get a go-to equatorial mount. And thank me later 😌 

 

[WolfieGlos]

1 hour ago, 900SL said:

And trying to find and frame targets will have you pulling your hair out.

Oh yes, I forgot about that. Sometimes you can get lucky and manually locate the target in 20 minutes....I think my worst was over an hour trying to locate it, with plate solving via wifi from a camera to a phone. Then add framing the target into the equation...

I do not miss that. At all. Total waste of time.

I even recall at one point I was considering upgrading the wedge to the William Optics version because the SW one was so wobbly. By which time, you've spent the money for an EQ mount, with GoTo.

1 hour ago, 900SL said:

Those you tube influencers who promote this clockwork pot metal poor tolerance thingy have no morals.

I forget who it was, but someone had a video and was using the SA2i with a Sigma 150-600 lens....and it was suggested that they were using it at 600mm! Absolutely ridiculous.