? Stacking problem, ? What problem?

[Stridor]

I'm just starting a bit of imaging; with some great help on SGL I managed to get Deep Sky Stacker 3.3.4 downloaded and stacked the image of M37 in Auriga: this was about 20 exposures on an unguided scope; I was pretty pleased with the result which I have enclosed. So, full of optimism I went out last night and attempted to image M81 & M82; something like 30 exposures. I downloaded the images onto the computer and all the Thumbnails looked ok, so I thought they looked promising; however, when processed & stacked in DSS I have ended up with pretty much no image at all. As I say, this is all new to me, but if I moved the slide controls (top right on DSS) to the extreme left I had a very blurry image with star trails!? The M37 image was very straightforward, so I'm a bit mystified with what appears to be a total flop. What have I done wrong? As usual, any help is appreciated.

[PeterCPC]

DSS does not like star trails but you say the individual subs are OK?

Peter

[Stridor]

Individual subs are all fine; or what I would call fine!

[PeterCPC]

Have you tried stacking just a few subs to see what happens?

Peter

[Stridor]

37 minutes ago, PeterCPC said:

DSS does not like star trails but you say the individual subs are OK?

Peter

 

37 minutes ago, PeterCPC said:

DSS does not like star trails but you say the individual subs are OK?

Peter

 

16 minutes ago, PeterCPC said:

Have you tried stacking just a few subs to see what happens?

Peter

Yes, that was actually my first (and only!) thought.......same result though!!??

[PeterCPC]

Presumably you stretched the data in DSS by moving the saturation up to say 15%, bottom luminance to 100% and middle luminance to around 37% and moved the RGB to 1/3 of the way into the graph. If you did all that then I am at a total loss.

Peter

[Freddie]

Can you post up a single sub and the stack so we can have a look. How many starts does DSS say it has detected?

[Stridor]

27 minutes ago, Freddie said:

Can you post up a single sub and the stack so we can have a look. How many starts does DSS say it has detected?

If you could let me know how I get the RAW sub and stack onto SGL I will gladly do it as the finished 'stacked' image looks like I took it 'hand held!!' It will probably be at least tomorrow before I can do this as I have to get ready for work soon.

[Stridor]

2 hours ago, Freddie said:

Can you post up a single sub and the stack so we can have a look. How many starts does DSS say it has detected?

I have 30 subs with a pretty even range of between 56 & 136 stars.

[wimvb]

Sometines stacking software will align on hot pixels. Since these are always in the same place, you should get dx and dy values of 0.0. You might check this first. If this is the case, you need to adjust stacking parameters or use cosmetic correction.

Hope this helps

[wimvb]

Sometines sracking software will align on hot pixels. Since these are always in the same place, you should get dx and dy values of 0.0. You might check this first. If this is the case, you need to adjust sracking parameters or use cosmetic correction.

Hope this helps

[Stridor]

22 hours ago, wimvb said:

Sometines sracking software will align on hot pixels. Since these are always in the same place, you should get dx and dy values of 0.0. You might check this first. If this is the case, you need to adjust sracking parameters or use cosmetic correction.

Hope this helps

Thanks; I have set the dx dy value to 0.0 but only end up with one image out of 30 which is stackable!!??  As I say all the subs look good.  As someone who has been a visual observer only, and always been wary of venturing into the field of Imaging, I am now wishing I had not been so hasty in buying a more suitable camera + a Focal reducer/Field Flattener; these may have been bad buys?  No matter how I tweek things with my subs and DSS I only end up with a foggy image with star trails. It appears at the moment that all I can do is save one sub, and treat that as `my image!!`........DSS does not appear fit for purpose! Very, very disappointed.

[wimvb]

dX and dY values shouldn't be anything you can SET. The values are calculated by DSS when it does the image alignment (registration). Although your AZ EQ6 is a good and stable mount, there will always be a little shift between light frames. Stars are shifted in X and Y direction, and maybe there is some rotation as well. DSS will report these values in the image file list of the main screen. If you find that all images have reported dX and dY of 0.0, this means that according to DSS, there was no shift att all between exposures. In that case, DSS most likely, took hot pixels as stars.

I noticed that your M37 image has slight defocus. It's quite a while since I used DSS, but if I recall correctly it doesn't like out of focus stars. In the M37 image there are so many stars to pick from that DSS probably could handle it anyway. In the M81 image, if there are fewer stars and they are out of focus, DSS may fail to do a proper alignment.

My advice: examine your raw image files. If stars seem ok, use the Cosmetic Correction function in DSS (its in the options > Settings > Stacking Settings ... > Stacking Parameters, right next to the Intermediate Files tab). BTW, also make sure that in the same Stacking settings, under the Alignment tab, the checkbox next to No Alignment is NOT checked. This is easy to miss.

Good luck,

 

[Stridor]

19 minutes ago, wimvb said:

dX and dY values shouldn't be anything you can SET. The values are calculated by DSS when it does the image alignment (registration). Although your AZ EQ6 is a good and stable mount, there will always be a little shift between light frames. Stars are shifted in X and Y direction, and maybe there is some rotation as well. DSS will report these values in the image file list of the main screen. If you find that all images have reported dX and dY of 0.0, this means that according to DSS, there was no shift att all between exposures. In that case, DSS most likely, took hot pixels as stars.

I noticed that your M37 image has slight defocus. It's quite a while since I used DSS, but if I recall correctly it doesn't like out of focus stars. In the M37 image there are so many stars to pick from that DSS probably could handle it anyway. In the M81 image, if there are fewer stars and they are out of focus, DSS may fail to do a proper alignment.

My advice: examine your raw image files. If stars seem ok, use the Cosmetic Correction function in DSS (its in the options > Settings > Stacking Settings ... > Stacking Parameters, right next to the Intermediate Files tab). BTW, also make sure that in the same Stacking settings, under the Alignment tab, the checkbox next to No Alignment is NOT checked. This is easy to miss.

Good luck,

 

Thanks for the advice, tomorrow I'll have a look at the 'Cosmetic settings'. As a thought, would there be anything to be gained from me trying a different 'Stacking' software , e.g. Registax? 

[wimvb]

I have no experience with Registax, but others use it with good results. You can also download PixInsight for evaluation. PI isn't cheap, but it can do all processing. The evaluation version is valid for 45 days.

In DSS you could also try restacking your M37 subs, which you know worked ok. Examine the stacking output (i.e. the information in the file list)

 

Cheers,

[Freddie]

Registax isn't designed to stack DSO images. DSS will work fine, it's just a case of knowing how it works and what it can and can't do. Posting up the M81/2 data will help. You posted up your M37 pic so just do that again with the M81/2. You can post up as TIFF or PNG. TIFF would probably be easier as you can save those from DSS.

[wimvb]

3 minutes ago, Freddie said:

Registax isn't designed to stack DSO images. DSS will work fine, it's just a case of knowing how it works and what it can and can't do. Posting up the M81/2 data will help. You posted up your M37 pic so just do that again with the M81/2. You can post up as TIFF or PNG. TIFF would probably be easier as you can save those from DSS.

Sorry, mixup. RegistaR is used for DSO