IDM

The nights are now getting very short for me with only a short window for gathering data. So this is probably my last image before the days start top shorten.  I have attached 2 images the first being the total data gathered over 5 nights between the 26th of April and the 1st of May. Combining everything over these nights gave me about 11 hours worth of 90 second subs. The second image consists of only selecting the subs taken between 23.00 and 02.00  ()about 5 hours total data) on the nights and therefore represent the darkest parts of the nights. I tried to process both these data in a similar fashion to try and see if I was better off  with 5 hours of darker background or more 11 hours but risking some non astronomically dark data. To be honest I am unsure which is best, I think the 5 hour data set probably is but interested in peoples thoughts.

Imaging was done with a Celestron C8 with Meade f6.3 reducer, Camera was a Zwo ASI294 MC pro. I used NINA acquisition software with PHD2. The telescope was mounted on a Zwo AM5. All stacking and processing was done using Pixinsight.

Thanks for looking

A new toy arrived with less than 24 hours between buying online and delivery from Altair. 
managed to get it to fit to my Skywatcher Equinox using the supplied fitting kit. I also like the fact that it has buttons for in and out so don’t need extra handset or to use computer to get approximate focus.

3 minutes ago, Elp said:

Yes, as the vignette profile will likely change. I've got the C6/C8 shield, think it's the same as yours but my scope is C6. I find prior to imaging I have to be absolutely sure that the shield is square in both axis to the central axis of the scope (x and y if you're looking right at the corrector plate face on) or near enough as you can make it, and make sure the cutout is butted up to the start of the dovetail and that the circumference of the shield is fairly snug. This serves two purposes, as I point my scope directly up to take flats and rest the panel on top of the dew shield, so the shield doesn't move. I have on occasion had it shift but luckily the flats worked fine once I shifted the shield back straight. It's not an ideal method, and with your C8 the panel will be heavier.

I've thought about getting the aluminium dew shield to mitigate this issue but it's not exactly cheap. In the meantime I've got ND film to wrap around my panel so it's lighter to put on top of the dew shield then with the perspex I'm using currently, this may sort my problem.

But yes, you need to keep the optical path the same as your imaging conditions. It doesn't matter if light leaks out onto the sides of the outside of the shield as long as the panel is flat to it, covers it, and the dew shield is wrapped sufficiently around the OTA body that you don't get light leaking into it from underneath.

Superb advice. I will make the changes and try again

Many thanks,

Ian

Just now, Elp said:

What dew shield?

The standard Celestron Velcro one. Though, I have been wondering if that's part of the problem as I have taken the flats without the dew shield, is that wrong?

1 minute ago, Elp said:

What scope it is?

Problem occurs with my C8 SCT with f6.3 reducer

51 minutes ago, Xilman said:

Do you have any evidence that the flats you take are unsatisfactory? That is, do you see any residual gradients, vignetting, etc after applying your flats to your lights?

Unfortunately, I am seeing vignetting, this doesn't seem to happen with my refractors it is something that has become worse when trying to take Flats with my C8 SCT. Currently Graxpert is doing a good job of sorting it out, but that clearly isn't the best approach!!

16 minutes ago, Elp said:

Your camera settings should be the same as the lights (gain, temperature etc) the only thing you adjust is the exposure time to get the histogram as you want it. If it's too bright very quickly you need to diffuse the light even more.

That's very helpful, so don't touch the gain just dim the panel with more layers . I am thinking that this is likely to need tp be very dim and therefore even with the light panel on the end of the scope there will need tp be some sort of seal to  prevent stray light creeping round the edge, or take the flats in total darkness. Would that be right?

M106 taken using my Celestron C8 with Meade 0.63 reducer and a Zwo ASI 294 MC pro camera. Capture software was NINA with PHD2 for guiding (separate guide scope currently being used).

A total of 239 90 second subs taken at bin 2. The subs along with flats, darks and dark flats were stacked with Pixinsight using weighted batch pre processing. All subsequent steps were performed using Pixinsight to get the final image.

I am still not sure I have the C8 optimsed properly with the back focus from the Meade reducer. Additionally I have convinced myself that my flats are not right as there was a lot of vignetting and. some rather odd halos concentric to the galaxy.

The capture was probably not helped by a rather prominent moon, but if I waited for clear skies and no moon I wouldn’t capture anything!

Thanks for looking

Ian

I have been using flats for several years but recently was wondering if maybe the flats I was taking might not be as good as they possibly could. My current method is to use a light panel with several sheets of white A4 on top to dim the light source. I then adjust both the gain and the exposure time so that I can achieve an exposure time in the region of 1.5 seconds and the histogram at or around 50%.

In order to see if I was doing anything wrong or if my results could be improved I had a look around the web and seemed to find some conflicting information. Some sites state that the camera gain should be the same as used to capture lights. The problem I have with this is that if I keep the gain the same I end up with very short exposure times if I am to keep the histogram at or around 50%. This then conflicts with other online advice that states that flats exposure time should be somewhere in the range of 1-3 seconds.

Given I have spent hours optimising and capturing data I don’t want potentially reduce the quality of my processed image through poor calibration. Therefore What do people consider to be the best way to capture flats?

Thanks,

Ian

I was very excited when I first processed the image as I felt I was making some forward steps and I certainly appreciate all the feedback that will hopefully help me improve still further in the future. Though at times it feels like the more I learn the less I know 🙂 but I think its part of what makes this hobby so fascinating and possibly addictive, as there is always room for experimentation and improvement.

Thanks,

Ian 

9 hours ago, 900SL said:

Very nice M51 IDM, and well done for a first image with pixinsight! The C8 looks like a good un!

Thanks for the positive comments.

On 09/04/2024 at 14:17, tomato said:

Excellent detail, and subtle processing of the colour. I'm always tempted and usually succumb to overdoing the saturation on this galaxy. I agree with Olly that there is a hint of green overall on my monitor, but it's not much. 

Thank you for the kind feedback. I am trying to be more subtle with my images. In planetary my enthusiasm used to get the better of  me so I am trying to be cautious to achieve less  = more.

Ian

@ollypenrice Thank you so much for the comprehensive and really helpful feedback I will have to spend some time digesting and learning.

Ian

On 09/04/2024 at 09:04, AstroMuni said:

Stars look quite nice & round across the whole image so I would have been very happy with this setting. Lovely image with lots of detail.👍

Thank you for the kind words.

Last year I bought a C11 for planets which had a Celestron dew ring heater and it has been really successful in controlling dew. Indeed I have been using it without a dew shield with no problems. Just the other week I picked up a C8 with an F6.3 flattener/reducer for galaxies. I have only tried it once (I just posted my M51 image in the DSO imaging section). I haven’t sorted all its issues particularly with the reducer but it seems a good scope. I bought my C8 secondhand it was cheap and it’s quite light.

cheers

Ian

I recently acquired a Celestron C8 XLT with a Meade flattener and this image was taken on its first outing. I am not very confident about the Meade F6.3 reducer/flattener as the back spacing seems difficult and certainly I had very bad vignetting across the image that required a heavy crop prior to back ground extraction. Just to make my life more difficult the night I took the images I also decided to migrate from Sharpcap to Nina. Nina seems excellent but it didn't seem so intuitive as Sharpcap, though it handled the meridian flip with my Zwo AM5 perfectly (I followed Cuiv's settings from Youtube). 

So in the end I ended up with 217 90 second exposures using the C8 with Meade reducer and a Zwo ASI294 MC pro camera. Guiding was provided by Skywatcher finder-scope I converted to guidescope, focal length 185mm (approx.). It's not the best but I felt for a first outing I was pleased. Processing was done using a newly acquired Pixinsight license, so again I am at the bottom of the learning curve!!!

Since taking the image I had a look at the Collimation and with a backspacing of 105mm I noticed good collimation at the centre but put poor round the edges. So I don't things are right. I have since reduced the backspace to about 75mm and the collimation looks better across the sensor. The weather hasn't been great since the change so I haven't been able to test it by imaging properly, though I did do a plate solve and Nina (ASTAP) reported a focal length of 1336mm which seems a little long.

I would be grateful for all thoughts on the reducer and helpful feedback on the image

9 hours ago, Flame Nebula said:

715mc be useful for dso with an Ed80, (at F6

Whilst it will work it’s not great as you will be considerably over sampled. The easy way to check telescopes with different cameras is to use this online calculator:

https://astronomy.tools/calculators/ccd_suitability
 

It suggests the combination is not good also the lack of cooling doesn’t help. Though I do know some planetary camera are better than others with regard to long exposure DSO work, I am afraid I don’t know which would be best.

Ian

38 minutes ago, blinky said:

It should be 110mm if I remember correctly

I have currently set it at 105mm. Tomorrow I will try measuring the focal length as suggested by @michael8554

6 hours ago, michael8554 said:

Measure its focal length by focusing the sun (what sun ? 😆 ) onto a wall.

If it's around 210mm, adjust for best star shape in the corners, starting at 105mm Back Focus.

If the FL is about 135mm, start at 85mm Back Focus.

Rumour has it the the sun may come our here (briefly) tomorrow so I will try as you suggest.

Thanks for the help.

Ian

9 hours ago, Cosmic Geoff said:

The back focus (with the Celestron f6.3 reducer) is not that critical

That's good to know as I guess the Meade is similar in design. I am just used to trying to be very precise with flatteners for refractors so it goes against the grain for approximate measurements! 

I recently obtained a secondhand Celestron C8 and Meade focal reducer/flattener and am now searching around to try an find details on the back focus for the Meade reducer. There are many posts saying its not the greatest reducer on earth but little on back focus. One post on Cloudy nights suggested 105mm. I had a look on the Meade website and despite listing the reducer I could not fins any instructions or guidance documents. Does anybody know the correct answer or have any guidance? I am interested in trying the scope with reducer as a reasonably fast scope for galaxy astrophotography.

Thanks,

Ian 

Just an update as I now have the firmware upgrade sorted. I contacted QHY and raised a ticket and I have to say they couldn't have been more helpful. They asked questions and I answered, there responses always being within 24 hours. Ultimately they couldn't see what I was doing wrong so they asked me to download Anydesk onto my PC and give them permission to do the update for me remotely which they did and it worked. Excellent support.

It appears that for reasons I don't understand the Hex file needs to be on your desktop not in a folder. If it is in a folder, even it you navigate to it, the upload fails. Hope this information might help someone else trying to do the upgrade.

Cheers

Ian

My first attempt at the Rosette neubula with my new QHY268MM camera and using Astronomik narrow band filters. Image consists of:

19x 180S Ha

50x 180S O

50 x 180S S

The images were captured on the 14th and 15th of January.

Processing was me watching some videos on Youtube and 'just having a go' (much to learn) but its a a start!!

2 hours ago, GasGiant said:

Is this it ? Looks like its was made in the early 90s ?

My pc is saying its unsafe to download ?  

It’s a while since I downloaded it but yes I think that’s the site. The software doesn’t look like that when installed. I cannot recall warnings about safety but it was fine. I also know many people use it for planetary.

Ian

You might want to consider trying Astrosurface as another free software package. I think it gives you greater control with both wavelet sharpening as well as other sharpening tools. I have used it mostly with my more recent Jupiter images and found it very useful.

Ian