sshenke

Had a very narrow window to image the sun yesterday, and was lucky to get full 60 seconds of video before the clouds rolled in!

18 minutes ago, almcl said:

You seem to have got a lot of groups (4 in the screen shot). 

If the darks and flats are in different groups to the lights they won't be stacked. 

Try putting them in the same group as your lights, if they aren't already?

almcl, thank you so much.  Your solution works.....!!!  have a great day!! btw, can I ask what the purpose of those group tabs is.

9 minutes ago, Adam1234 said:

The only other thing I can think of then is ensuring that you're dark and flats match the light frames. Sorry I can't be of much help

ok, thanks. They do match. very frustrating indeed

2 minutes ago, Adam1234 said:

Have you registered the files?

yes I did, then selected a reference frame  and then re-registered using teh reference frame

Hello, can someone help please. Deep Sky Stacker is not processing my dark or flat frames at all. Even though it recognises it when first added, it doesnt produce master files and when I start the stacking process, it says that there are no dark or flat frames as seen in the attached screenshot. Not sure what I am doing wrong. Would appreciate your help. Thanks

2 hours ago, MartinB said:

The arc artefact is adjacent to a darked part of the image.  I wonder if your filter  wheel isn't rotating properly.  This could cause the small arc as a result of reflection and the dark edge.  If you can it is worth having a look at how accurately the wheel is placing the filters.  

Thanks, I will look at the rotation of the fw.

Had very clear skies last night, but did not get any proper images at all. I can see the arc more clearly in the pictures of the pleiades and I can see the same sort of smudge in the picture of M33 ( that picture is a 120 sec exposure of M33!!!!).  Looking through the objective port of the scope, I noticed that the secondary mirror is off centre, so I think collimation is definitely a problem. I can also see the bevelled edge of the secondary mirror being prominent and I wonder if there is light coming from the primary mirror that is being reflected off this bevelled edge on to the camera causing the arc. 

1 hour ago, souls33k3r said:

Could it possibly be dew forming on the camera optical window?

I am not sure if thats the case, because of 1. why would the dew always form on the same place- the optical window of the ccd camera looks clean to me 2. If it is because of dew, I would expect the images on the second round to be worse because of dew getting worse the longer the scope is outside. This is what I think, may be I am wrong, but thanks for looking into this issue. Really appreciate it

8 minutes ago, carastro said:

Is this the only target you have tried this with?  Just wondering whether is is some sort of reflection. 

Carole 

Thanks Carole, yes this is what I have been targeting primarily, as it was an easy target to acquire, given the problems I have been facing. But I did try a few other things like veil nebula, but have not been able to do any substantial imaging with these targets because of the cloud cover. I am going to try again tonight with a differ ent target

Hello all, I would appreciate your help on this problem please. I have been having a huge problem with capturing dso images since October last year, having previously managed to obtain good images of a few galaxies and nebulae ( I started doing this in July last year). For the last few months though I haven't captured even a single decent image and have been blaming the dew, refractor, filter etc. But finally I seem to have got to the bottom of it or so I think. As you can see in the attached images, there is a crescentic area of artefact near the centre of the image. Initially I thought it was the filter, but when I imaged without the filter, it is still there. I cannot see any obvious problem in the optical window of the CCD sensor, but still cleaned it properly with isopropyl alcohol and went onto test it last night and noticed this weird thing. I took 2 round of  1 frame each of lrgb images of m31. I didn't touch the scope or the capture software until the 2 rounds were completed and what I notice is that the smudge was there in round 1 images ( postfixed 1..red1, green etc), but not in round 2 images. I am not sure if it is due to drop in visibility as there was some cloud cover during round 2. Also I cannot see this artefact on images taken during daytime, such as of the sun. It moves independently of the image with the movement of the telescope, which is why I think it is on the CCD camera. This is ruining the images significantly and the unpredictability of it occurring is another frustrating thing. Would appreciate the help of the experienced and the wise please. The image with the title of andromeda 1 was taken about 2 months ago. I have also previously cleaned the primary and secondary mirrors thinking that that's where the problem was. 

Scope: sky watcher 130 pds

Zwo asi 1600mm camera

Thanks

Thanks Vlaiv and Billy, I will switch to the 16 bit mode tonight and see if that makes a difference. What do you think about the histograms of the asi1600 and asi120, in the images posted above?. I never get a good histogram with the 1600.  as for the dew heating, yes i have used a circular heating pad ( they use it for brewing!!!,) to the back of the primary and it stopped dew from forming, although now i am wondering if dew was present in the primary at all.

Hello all, I have been struggling to obtain good images for some time now, which I have asked help with for , as in the following post:

https://stargazerslounge.com/topic/342321-poor-image-quality-cause/

I thought that dew was the problem, hence I posted in this thread discussing about the merits of buying a refractor instead. Previously I was absolutely certain that there was dew on the primary mirror, but I am not sure now. In fact the dew that I noticed on the primary mirror was seen as soon as I had brought the telescope indoors, so it is very likely that the dew had condensed on the surface when it was brought indoors rather than while it was outdoors.

Last night has been another disastrous (sorry for the pun!) session where I could hardly see the M31, this is really perplexing to me. Interestingly, the guidescope seems to produce better image than teh main camera as you can seen from the attached images: The ASI 120 mini is the camera attached to the guidescope and the ASI 1600MM pro is the main camera attached to the telescope- skywatcher 130PDS. For the same exposure time, or even less, the guidescope camera collects more light than the main camera. I am guessing that this shoudl not be the case? I wonder if anyone can shed light on this problem please. Thanks in advance

10 hours ago, dannybgoode said:

Yep-something about Kruppax isn’t there?! Magic stuff, doesn’t seem to matter what the temperature is or whether you move the scope from somewhere cold to somewhere warm or vice versa, there’s not a drop of dew. 
 

Not entirely sure how the tube material has such an effect on the glass of the objective but it works. 
 

To OP - the corrector lens on my SCT dews up before any other glass on any of my scopes and I simply can’t shift it. Very frustrating when you’ve got everything set up nicely and then your evening is ruined. 
 

One suggestion-have you cleaned the primary? Dust etc will exacerbate dew issues as the water has something to saturate and cling to. 

i was thinking about cleaning the primary mirror as well, although it doesnt look too dirty.

Thank you both. there are no water bodies nearby and i can't think of any local factors that might impact on dew formation.

9 minutes ago, John said:

I think dewing depends to some extent on location. At home I hardly ever have dewing problems with my refractors but at my society observatory (about 6 miles from my home) I need to use dew shields.

SCT's and maksutovs need dew prevention even at home though.

My Kruppax tubed 130mm frac seems to be totally immune from dewing - apparently something to do with the properties of Kruppax.

I am not sure if it is anything to do with location. I live in  the Midlands ( milton keynes). 

1 hour ago, dweller25 said:

Interesting that the guidescope does not dew up - is it heated ? They are usually the first to dew up !
You did a great job lagging the scope but both ends are open - I would suggest you make a dewshield for the front of the scope and seal the rear of the scope once the mirror has cooled.

Thanks. I left the rear end open, so as to use the fan with or without heating mode, in case the wrapping didn't work. Will close it off as well and see if it works. Thanks. B

10 hours ago, astronomer2002 said:

This topic has just reminded me of my endless fights with dew on refractors, reflectors and SCT's.

Nothing really worked better for me than a long, cheap, black art drawing paper dew shield held on with elastic bands. Tried it out of desperation once when at a school outreach session and it stopped the sct from dewing up. The soft black drawing paper came from their  art dept! Worked better than any purchased dew shield!

Worst scope for dewing up I have at the moment is a truss RC. the main mirror goes almost as soon as the secondary. If I heat the secondary the main mirror still curtails observing. Open tubes in this country are a liability.

Don't imagine a refractor will be immune, I have had issues with these as well, though to be fair they take longer to dew up if they have decent dew shields. Once again the long art paper dewshield worked with them too even if they had long metal dewshields.

Ian B

Thanks Ian, i am going to try the diy dew shield as well

5 minutes ago, Louis D said:

Don't be so harsh on yourself.  That's actually pretty nicely done job of wrapping the tube.  Too bad it didn't mitigate the dewing.  You must live in a very damp region.  Do you often get morning fog?

Do you get any dewing on the guide scope's objective lens?

Thanks, well for what it's worth, I have wrapped the tube, even if it looks absolutely ridiculous!! I had checked the guidescope objective on last Monday and actually it did not have any dew on it.

36 minutes ago, carastro said:

Yes, but in the winter I was inside an observatory with dew heaters sometimes wrapped around the tube either side of the focusser as a precaution. 

Are you absolutely sure it is the primary that is dewing up, i.e. you have looked down the tube at the primary? 

Carole  

 

Yes, absolutely, i have attached a picture i took a few weeks ago looking down the ota

On 18/11/2019 at 18:51, joe aguiar said:

are you sure its the main mirror that has the problem tho?just saying since your using blowing the  main mirror.

if you are looking down the tube your probally not seeing the issue is the 2nd mirror and most likely not the primary, reason iam saying is I had this isse b4 too and its wasn't the primary since the 2nd mirror is sometimes only 2 or 3 inches from the front its probally that.

just using a dewcap that's like 10 inch is more then fine almost all times unless your outside for the whole night.

joejaguar

i understand what you are saying. i wondered about that too, as i cannot see what's going on with the secondary mirror. however, it is absolutely clear that the main mirror dews up within a maximum of 1 to 2 hours. I have been using a fan with heating option to blow air from behind the main mirror, not directly down the tube from the front end

28 minutes ago, carastro said:

I have been using refractors and dew heaters for 9 years and only time I had dew was when my dew heater failed.  I also had a SW130PDS for 2 years and never had dew on that either, but I was worried it could happen so I always had it inside an obervatory eitehr at home or a camping observatory and additionally drapped dew heaters around the tube (either side of the focusser), not sure if that helped or not.

My refactors have been out on the camping field loads of times and with dew heaters I never get a problem with dew.

Carole 

Carole, this is really puzzling for me, i have draped the sw 130 pds in exercise mat when i took it out on Monday evening. i will post the picture later, might be hilarious. Temp on Monday evening was 1 to 2 degrees at 8 pm. mirror dewed up promptly within 1 hour. never got to see a single image of interest. Can I ask, if the sw 130 pds you used, worked well in winter too?

On 18/11/2019 at 18:51, joe aguiar said:

are you sure its the main mirror that has the problem tho?just saying since your using blowing the  main mirror.

if you are looking down the tube your probally not seeing the issue is the 2nd mirror and most likely not the primary, reason iam saying is I had this isse b4 too and its wasn't the primary since the 2nd mirror is sometimes only 2 or 3 inches from the front its probally that.

just using a dewcap that's like 10 inch is more then fine almost all times unless your outside for the whole night.

joejaguar

i understand what you are saying. i wondered about that too, as i cannot see what's going on with the secondary mirror. however, it is absolutely clear that the main mirror dews up within a maximum of 1 to 2 hours. I have been using a fan with heating option to blow air from behind the main mirror, not directly down the tube from the front end

26 minutes ago, Carbon Brush said:

For me, it is about using the minimum amount of scope heat to prevent dew - rather than remove it.
That avoids the loss of focus from a hot air blast.

Generally I reserve the hot air for ensuring kit is warm and dry at the end of a session.

This autumn is though a bit different. The garden is really soggy and there is often almost 100% humidity on the (rare) clear nights.

HTH, David.

Thanks David, will keep trying!

On 15/11/2019 at 16:07, Carbon Brush said:

Dew shields, heaters and hair dryers are cheap.
Good refractors are expensive and still use metal & glass.

If you are happy with the 130 (apart from dew) why not preserve the wallet?

Just my random ramblings. David.

Thanks. I was certainly happy with the images produced using the sw130 PDS until a few months ago, but not any more as I have made hardly any image worth the effort I had put in, because of the dew problem. It is really puzzling to me as every post I have read says how rare it is to see dew in the primary mirror of a reflector. Not sure if I am doing something wrong. I have tried hair dryer and fan heater ( blowing gently from a distance of about 30 cm)  as well. Usually this leads to loss of focussing and it takes about 10 minutes to get the images back into focus, so not useful. I am going to try the insulation mat and dew shield/ cap idea as well next time there is clear sky, before deciding to buy a refractor.

I do have the book, electronic version, but must admit that I havent read it properly yet. It seems well written, glancing through the different chapters. Will read it at some point when I find the time. Happy reading!!

Thanks everyone for your helpful advice. Yes, the 130 pds has metal tube. I will cut out foam mat to cover it wherever i can. in terms of dew shield, i was informed that the ota tube itself acts as a dew shield for reflectors. I shall give it a go, but if it doesnt work, then will buy the refractor. thanks once again