The "No EQ" DSO Challenge!

[furrysocks2]

Tonight has been my very first go with an AltAz GOTO mount. I've got my Datyson T7M (ASI120MM) with a 50mm f/1.4 CCTV lens mounted to a couple of 3D printed parts, one of which was a repair to the mount so that I could actually do this. I'm sitting in the warmth, drinking herbal tea.

I took a couple of darks for different exposure/gain settings and shot a few targets but ended up selecting M52 for the rich star field in the rest of the frame.

Field of view is 5.82 x 4.36 deg at 16.4 arcsec/pixel. 100@32s at gain 2.

 

Field rotation is obvious over nearly an hour. Don't know if I got focus spot on or not, and 30s might be starting to push it.

 

[furrysocks2]

Followed by a comparatively quick 50@5s, gain 50 on the Perseus cluster.

[Peter77]

Hello,

 

I've been out again and having some fun.

Targets were M31 and Pleiades.

 

M31 a grand total of 65 pictures and Pleiades a grand total of 47 pictures. The bulk of them were 30 sek exposers, also mixing in a few 25 and 20 sek exposures. Varying between 1600 to 800 iso.

 

Gotta got my Bottom of the wagon to do some proper darks and flats, but quite happy with the results nontheless. Mostly with the Pleiades, nice colors. But it's nice to have captured M31 as well. It's been a dreamtarget.

 

Had a little lightpolluted area of the sky aswell but not too bad anyway.

 

Shot through Nexstar 102 slt on Alt-az goto mount with Nikon D3100 in prime focus.

 

 

Edited October 1, 2018 by Peter77

[Manners2020]

Hello all , bare with me why I try to make sense here. So the red shaded corners of the top image. Is that vignetting  from using a 6.3 reducer on a 9.25 sct? I'm hoping it's the red shaded bit and not either of the parts with the arrows.  I'm hoping the area with the arrows is a mixture of my lack of experience,  a 97% moon really close to the target and light pollution. Also this was done via astro toaster, now I'm currently using jpeg  fine and small just because my laptop handles it better and I'm led to believe  shooting raw wont really benefit me on astrtoaster. I'm going to try fine and large next time when weather permits. Any thoughts on how that will affect the image? The camera is a d5300 . Thanks.

[happy-kat]

That's not obvious vignetting. If you remove the focal reducer do you still get that pattern?

@Peter77 the extra exposures are helping to control the noise, I'd next time resist changing target and go for maximum on the one target.

@furrysocks2 what did you use to create your graphs please? That's a busy constellation. Your camera and lens must be super light on your mount.

Edited October 2, 2018 by happy-kat

[Peter77]

42 minutes ago, happy-kat said:

That's not obvious vignetting. If you remove the focal reducer do you still get that pattern?

@Peter77 the extra exposures are helping to control the noise, I'd next time resist changing target and go for maximum on the one target.

 

I will try a larger bulk of exposures along with flats and darks as well. I was actually done yesterday and on the way to take the gear in. And then I saw the pleiades and thought "hmm", let's try a few shots at those also. 

Andromeda proved to be a quite hard target to get the colors right. It would be fun to try stack some different sequences of the pictures I shot. This time I stacked them all. 

 

But yes, I will definitely give Andromeda another shot.

 

By the way, I managed to get much of the red out of the double cluster picture.

 

Putting both up for comparison. I liked the vibrance of the first picture but there was too much red in it.

 

[furrysocks2]

2 hours ago, happy-kat said:

what did you use to create your graphs please? That's a busy constellation. Your camera and lens must be super light on your mount.

The graphs are on the "Drift Graph" tab in SharpCap's live stacking.

Pretty minimalist set up, yes!

[happy-kat]

 

2 hours ago, Peter77 said:

I will try a larger bulk of exposures along with flats and darks as well. I was actually done yesterday and on the way to take the gear in. And then I saw the pleiades and thought "hmm", let's try a few shots at those also. 

 Darks with a DSLR can prove to add more noise and they take up valuable time. I would try flats and dark flats first they help with vignetting and noise.

[Stub Mandrel]

2 hours ago, Peter77 said:

I will try a larger bulk of exposures along with flats and darks as well. I was actually done yesterday and on the way to take the gear in. And then I saw the pleiades and thought "hmm", let's try a few shots at those also. 

Andromeda proved to be a quite hard target to get the colors right. It would be fun to try stack some different sequences of the pictures I shot. This time I stacked them all. 

 

But yes, I will definitely give Andromeda another shot.

 

By the way, I managed to get much of the red out of the double cluster picture.

 

Putting both up for comparison. I liked the vibrance of the first picture but there was too much red in it.

 

If you have photoshop the 'gradient exterminator' plugin is excellent for getting rid of any residual vignetting or light pollution gradients, but it has a second trick up it's sleeve. You select all the  bright areas such as the clusters or any patches of nebulosity and then invert the selection. If you have 'balance background' as well as a selection for getting rid of gradients, it will fix that sort of colour cast in one step. I've found it worth running it even when there isn't a visible gradient.

[Manners2020]

12 hours ago, Manners2020 said:

Hello all , bare with me why I try to make sense here. So the red shaded corners of the top image. Is that vignetting  from using a 6.3 reducer on a 9.25 sct? I'm hoping it's the red shaded bit and not either of the parts with the arrows.  I'm hoping the area with the arrows is a mixture of my lack of experience,  a 97% moon really close to the target and light pollution. Also this was done via astro toaster, now I'm currently using jpeg  fine and small just because my laptop handles it better and I'm led to believe  shooting raw wont really benefit me on astrtoaster. I'm going to try fine and large next time when weather permits. Any thoughts on how that will affect the image? The camera is a d5300 . Thanks.

No  I was racing against clouds that night. I'll try next time the weather permits  if it ever does.

[dcweather]

I've just started out so a bit of a learning curve but thought I had a reasonable grasp. Then near the beginning of this thread someone posted an image from a Pentax DSLR with a 55-300mm lens at 300mm. It was a number of long exposure subs (~10 secs). Quite a good  image with no star trails. Even with stacking how could you achieve that? Alignment must be impossible? I thought you would have had to have  had a tracking mount for long exposures at 300mm?

[The Admiral]

3 hours ago, dcweather said:

I've just started out so a bit of a learning curve but thought I had a reasonable grasp. Then near the beginning of this thread someone posted an image from a Pentax DSLR with a 55-300mm lens at 300mm. It was a number of long exposure subs (~10 secs). Quite a good  image with no star trails. Even with stacking how could you achieve that? Alignment must be impossible? I thought you would have had to have  had a tracking mount for long exposures at 300mm?

I think that the Pentax has sensor shift image stabilisation which is able to be used to correct for star movement, within limits. May be that's how it was done, though I'm not familiar with that post.

Ian

[Stub Mandrel]

3 hours ago, dcweather said:

I've just started out so a bit of a learning curve but thought I had a reasonable grasp. Then near the beginning of this thread someone posted an image from a Pentax DSLR with a 55-300mm lens at 300mm. It was a number of long exposure subs (~10 secs). Quite a good  image with no star trails. Even with stacking how could you achieve that? Alignment must be impossible? I thought you would have had to have  had a tracking mount for long exposures at 300mm?

Most images on this thread are with Alt-Az tracking mounts. They can go up to about 30 seconds before field rotation becomes an issue.

[dcweather]

1 hour ago, The Admiral said:

I think that the Pentax has sensor shift image stabilisation which is able to be used to correct for star movement, within limits. May be that's how it was done, though I'm not familiar with that post.

Ian

The K3ii and K1 have a built in GPS astrotracer and some have an optional add on.  This was  "Pentax K-30, 55-300DAL zoom (@300mm) 30x10sec ISO6400, 5x10sec dark frames. Shot last night after 2 weeks of clouds  ." so probably was  tracked non-EQ. I had mis-read the thread and thought there was no tracking at all. 

[dcweather]

1 hour ago, Stub Mandrel said:

Most images on this thread are with Alt-Az tracking mounts. They can go up to about 30 seconds before field rotation becomes an issue.

Thank you. I'd wrongly interpreted the thread as no tracking and static stacking only.

[Stub Mandrel]

1 hour ago, dcweather said:

Thank you. I'd wrongly interpreted the thread as no tracking and static stacking only.

No worries; although I haven't taken any qualifying images I started out with an unguided EQ3 mount and this thread was biog inspiration for what could be achieved with short exposures.

[Manners2020]

Hello all.  This is probably  a stupid question  but it's one that's been nagging me. If stacking is to increase signal to noise ratio what's the reason we cant take 1 exposure  , make numerous  copys and stack them, or am I just making assumptions  and we can? Thanks. 

[happy-kat]

So stuff is just too faint to be picked up with 1 second so doesn't matter if there are 1000 1 seconds they still won't see it.

[Manners2020]

Well I was thinking more like copying numerous  30 second exposures.  All I can come up with is maybe  a raw cant be copied  with the same qualities  but I've never tried.  

[Manners2020]

I dont mean numerous  exposures  but copying  the same exposure  many times. 

[happy-kat]

Unless you manually effect a drizzle to each copied file the same pixel will have the same definition so won't get you more, as far as I know.

[Manners2020]

Thanks. I can stop wondering what if now.

[dcweather]

I think if you just had lots of the same image the noise will be fixed in each image and so you will always subtract the same amount from the same signal so end up with the same. With a number of images, because of the random nature of the noise, more of it will be removed from the background. Also with lots of images the dynamic range may be increased allowing e.g some of the faint pixels to be occasionally brighter and accumulated. I expect their other reasons.

[Manners2020]

That makes sense to me now.

[Manners2020]

First time seeing a glob. M13 I only stacked 5 30 second exposures.  Not sure if the 5 was better than the 1 but hey ho.