Aetherum

Hi there, fellow light-gatherers!

It has been a while since I posted here and I'd like to present you my first take at the Messier 3 globular cluster, or M3 for short, which was the very first object discovered by Charles Messier himself dating all the way back to the 18th century, 1764. Interestingly enough, Messier was convinced that M3 was a nebula at first until the equally famous and fellow contemporary astronomer William Herschel found that the object could be resolved into individual stars 20 years later, by which it was then declared as a globular cluster in 1784. M3 contains more than 274 variable stars, which is the highest number found among all globular clusters known to date. Globular clusters play an important part in the field of physical cosmology as they can be used to study stellar evolution in the early universe, as well as estimating its age.

I used my 102mm achromatic refractor on a motorised Alt-Az mount with two-star calibrated tracking. I took consecutive 30-second shots amounting to only 180-seconds, or 3-minutes of total exposure time, shot in my garden right in the city center of Ghent.

I know it is only 3 minutes, which isn't considered much in DSO imaging, but does it really make that much a difference apart from having a slightly brighter image due to less noise?

I kindly invite you to follow me on Instagram so I can see your work as well: https://www.instagram.com/eoasphotography/

#nightphotography #astrophotography #nightsky #stars #globularcluster #messier3 #messier #m3 #ghent

On 26/04/2021 at 16:47, Rusted said:

I have taken the liberty of pushing your image through ImPPG and Photofiltre.

Stacking would have helped too but I don't have your data.

 

Rusted, thanks man, that's pretty cool! Although, I find it's pushed too far. The edges are no longer smooth but really nice detail on the spots!

On 26/04/2021 at 16:46, happy-kat said:

SIRIL stacks and runs on mac os

I already got it, thanks! I'll try it out soon.

On 24/04/2021 at 13:55, malc-c said:

Geoff,

The issue of field rotation tends to be less noticeable when wide field targets are selected and wide field lenses or scopes are used.  It's quite surprising just how fast we are rotating, and even in a 3 minute exposure stars will trail.  Because an ALT/AZ mount has to make up / down / left / right movements when tracking it can lead to poor quality results when used with higher magnifications or long focal length scopes.  Imaging is possible with an AZ mount, but there are restraints that make it just a little more challenging.

Software can help, and stacking images, either live or post session, and it's just a case of how well the software can deal with the rotation and overlap the points of light.

Thanks for the advice. Do you have any advice for software I can use on macOS?

On 24/04/2021 at 16:24, happy-kat said:

M42 with your mount and ST202, it's on this thread, an example.

https://stargazerslounge.com/topic/228101-the-no-eq-dso-challenge/?do=findComment&comment=3776550

As you are using a DSLR I would take lots of images and use deep sky stacker to stack them and then process the output in something like GIMP to start with.

 

 

I'll try M42, but I'll have to find stacking software that will run on macOS. Thank for the tip

On 24/04/2021 at 11:04, Cosmic Geoff said:

I don't know the technicalities but basically it adds the exposures and discards shots that cannot be synchronised (not enough stars, etc)  It will compensate for field rotation. 

I use Sharpcap and then increase the contrast in Adobe Photoshop Elements.

Thank you for the tip. Unfortunately, I'm not running on Windows, so many applications I can't use. I only used GIMP so far and manual stacking wasn't a success. Great that it makes up for field rotation though..

On 13/04/2021 at 00:28, Cosmic Geoff said:

Aetherum - check this section to see what I imaged with the same 102mm achro scope as yours, and a basic alt-azimuth GoTo mount.

https://stargazerslounge.com/forum/123-eeva-reports/

On 13/04/2021 at 00:28, Cosmic Geoff said:

Aetherum - check this section to see what I imaged with the same 102mm achro scope as yours, and a basic alt-azimuth GoTo mount.

https://stargazerslounge.com/forum/123-eeva-reports/

Geoff,

Thanks for the tip, before I can image some galaxies I have to find them first. I hope that will be possible under these polluted city skies. How does live stacking work exactly, does it accumulate the individual exposures?

Kind regards,

Robbe.

13 hours ago, Luke said:

Hey Aetherum!

I have never done it but I would expect manual stacking in GIMP to produce poor results, quite possibly worse than the individual frames. I'd suggest to try Autostakkert, using hundreds or even thousands of alignment points:
https://www.autostakkert.com/

Then after you have stacked the image, try sharpening it using ImPPG:
http://greatattractor.github.io/imppg/

The result of stacking will probably be more blurry than the individual frames. However, it should also have far less noise, enabling you to apply a lot of sharpening to it.

I do think it is worth stacking 12 frames. I have stacked a similar number before and it made a difference for me.

How much the stacking helps will depend on how sharp the focus was and how good the conditions were.

I hope that helps and clear skies to you too! You can have some of mine as I have had a good run! I'd love to own a Russian scope one day, with some Russian writing on it somewhere! (I like the Cyrillic alphabet and love the sound of Russian).

Luke,

Thank you for your reply. I can't use autostakkert natively as I only run on Linux and Mac systems ImPPG likewise). I installed SiriL as an alternative but I haven't used it yet. I wanted to do manual stacking first to see how that worked out. The noise was likely reduced but very minimally, and the sharpness was reduced significantly. Just not worth my time. It seems like the increase in signal to noise ratio is negligible. 

The Russian MTO lens that I have looks quite similar to this one, I wonder if I can use it as a regular telescope with some kind of adapter for an eyepiece.

On 15/04/2021 at 09:23, wouterdhoye said:

Hi,

congrats on a fine first image.

For a single shot and using an achromatic telescope this is for sure a very fine image. 

for getting best results taking many many images and stacking is the best solution. For what i's worth, you can get autostakkert to work on a mac using crossover (an emulator) and that works fairly good, (it does lock up once in a while)

Kind regards,

Wouter.

Wouter,

Thank you! I'm sure stacking could improve the image, but with my last solar stacking experiment the results were rather contradictory. I will look into using autostakkert in Mac. However, I just downloaded SiriL as a Mac native alternative, but I haven't gotten into it yet. Any experience with that one?

Kind regards,

Robbe.

Hey Luke, thank you for your reply!

My setup was fixed and I actually had multiple shots but I just used the best one. Autostakkert doesn't work on Linux nor mac, so I'd have to do it manually. I don't see the use of stacking here because the opacity settings would just take away from the original image, so the result would still be 100% either way. I used GIMP to post-process. 

Clear skies to you!

Yes, I see how important the mount is in this case. But as said, I hadn't accounted for field rotation. Especially because my neighbor, which is an experienced astronomer, hadn't mentioned anything about it when I asked him about the mount. I know how aperture in terms of f-stops work. My 10.5 mm fisheye lens is an f/2.8, so that would gain some great results if I get the chance to shoot at a great location again. I'll just see what I can get with this, my camera is currently limited to 30-second exposures anyway. Thank you for your advice.

3 minutes ago, maxchess said:

All a bit on the long side for a AZ mount. Do you have a telephoto for the DSLR?

 

I thought fast refractors with an f-stop until about f/5 were perfectly ideal for imaging purposes? I have a kit lens with the D3300 going from 18 mm to 105, but at 105 the aperture is at 5.6. 

12 minutes ago, maxchess said:

You don't mention what lens/scope you have. If you are imaging on an AZ mount with a DSLR then you should concentrate on widefield targets using a focal length less than 200mm, which will tolerate less good tracking.  Also ramp up your ISO.  On targets like M31 etc you can get acceptable results with loads of 10 sec or less exposures.  But in the end there is no substitute for an EQ mount if you want to get into imaging.

I have a ST102 achromat, so 102/500 with various eyepieces. I have an ST80 as well, because that is the scope I bought originally, the ST102 came with the mount, but I will be selling it since the ST102 is just a better scope. I also have a cool vintage 10-1000 Russian Maksutov-Cassegrain lens, but that one isn't of much use for wide-field imaging. 

8 minutes ago, rotatux said:

AP with AZ tracking mounts has proved to be possible within certain limits and constraints, typ. with 20s-60s subs.

See / Search the (huge) thread here : 

for examples, techniques and general advice.

Cool! Thank you, quite interesting thread. 

I use a D3300 and I ordered a WiFi adapter to computerise my mount. And thank you, I'll look into it!

KP82, I wasn't aware that AZ mounts are prone to field rotation, but that makes a lot of sense. But I suppose the exposures can still be longer then without a tracking mount, at least? I don't know how that would translate in practice. 

Hi there!

I recently acquired an AZ SynScan GoTo mount to replace my AZ3 to do some astrophotography with an eyepiece adapter and a T2 ring. I'm still waiting on my battery to arrive, so I haven't been able to test it yet. But in awaiting the necessary accessories I starting looking up some information and I found that these mounts are not usable for astrophotography at all. Now, the issue at stake here is whether the vibrations of the motor would interfere with smooth tracking for high exposure times, and whether there are any practical solutions to eliminate said vibrations to any degree. Does anyone have experience with said issues or should I just go ahead and look for an equatorial mount? I thank dearly for advice of any kind!

Let the skies be clear.

Hi there!

It's been a while since I posted here and since my Skyliner 250PX is currently not at my own house, and since I'm getting into astrophotography, I acquired a nice little StarTravel rich-field refractor. I first had an ST80, but that one got replaced quickly by a ST102 because I found a GoTo mount second hand and the ST102 came with it. I decided to keep the ST102 due to the more aperture but still below the f/5 mark, especially with my 40 mm eyepiece I can enjoy extremely wide views.

Now, here comes the question. Like most people I dislike CA. Not that it is the end of the world, but I'm exploring means to reduce it and sharpening the image. I've looked into many different filters, such as the yellow #8 or #12, or the Baader filters, but are there any low-cost recommendations? Does the amount of CA differ among the same scopes due to the way they are collimated or discrepancies in the quality of the lenses? I thank dearly for any advice or recommendations.

Let the skies be clear.