CHR15

I like your set up! Is the tripod the standard skywatcher one which you colour coded red from white?

Do the u clips you use keep the telescope and camera in focus, can you post a link to the ones you've used?

Thanks.

20 hours ago, M40 said:

Certainly is 👌 I'm enjoying the simple setup, nice and straightforward. My plan is to try and get at least one new target every session, lets see what happens 🤣

That's a great idea, I still have to learn the best settings to use!

Nice shots, I stayed up a little later than normal to see the super nova a few nights ago.

The asi air is a great device ain't it?

2 hours ago, Lightfoot said:

Hi CHR 15

Having had the time to do some reading, I'm really leaning towards a set up similar to yours. The Dwarf 2 just doesn't inspire me and the Seestar doesn't start shipping until August, if then. I notice that you do not use a motorised focuser or filter wheel, do you not need them?

No counter balance either so I assume that the weight is well within the mounts capabilities.

As I'm still new I don't know much about the different filters but I've not used any and I just focus on a bright star before starting. I guess they can be added at a later date if you wanted them. 

Oops, I forgot to put the counterweight on 😆 I set it up to show you how compact eea can be. I only use a 1 kg counter weight, the ao70500 doesn't weigh anything, I bought a new to me st80 recently and this lightweight too.

With all the photos being took of the supernova in m101 I had to go and have a look!

bearing in mind this is from an eaa perspective and not been through photoshop, gimp, etc.

I decided to see if I could catch the north american nebula using my asi585mc camera combined with my st80. Unfortunately I couldn't, I also overexposed albireo too. M13 was a good hit though, I like how this turned out.

8 hours ago, Martin Meredith said:

If you search for fringe killer filters there are a few threads here and elsewhere that cover the specifics. I must admit I moved on to a reflector and gave the achromat away so I never explored these filters myself.

Gain is a simple multiplier that can be thought of as spreading the count of photons captured at each photosite (~pixel) across the bit range of the camera. Setting the gain is analogous to setting the recording level on a microphone amplifier. Set it too low and your recording occupies just the lower bit range, so you are not making effective use of the bits; while you can boost the resulting digital signal after you capture it, you are boosting a highly-quantised signal, which ends up sounding louder but also noisy. Set the gain too high and you are in danger of saturating. Setting the gain is a bit of an art.

[Aside: forcing a user to set the gain is a hack due to the low bit depth of most CMOS sensors.... personally, I prefer 16-bit CCD cameras with fixed gain -- one fewer decision ;-)]

Thanks for explaining things through thouroughly

1 hour ago, Steve in Boulder said:

Yes on bias.  You want the camera to be in total dark.  

The auto histogram on the ASIAir app is a good starting point, but you can do a lot better manually.  Expand the histogram using the button on the right.  Typically you want the black point (left slider) to the left of the histogram peak, and the right slider (mid point I think, not sure because ASIAir docs don't say) pushed to the left enough to show the features you're looking for.  

Unfortunately the ASAir app doesn't have hot pixel correction, so you'll probably want darks.  The dark sub exposure time should match your lights, i.e. 10 seconds.

Thanks for clearing up the bias question.

I'll have to have a play with the histogram too. Left pointer, left of the peak and right pointer, either middle or right of the peak.

At the moment I don't get hot pixels but it'll be good practice to take darks just to rule them out in future.

1 hour ago, Steve in Boulder said:

 

As Martin mentioned, darks are also helpful for hot pixels.  You can tell if they're a problem by looking for little streaks of color.  As also mentioned by Martin, your live stacking software may have a hot pixel correction feature.

It's helpful to know the gain as well.  Here's a useful explanation about gain.  50 x 10 seconds is a bit more than 8 minutes, which is a typical amount for EAA but you do have to expect some noise, especially if you stretch aggressively to show fainter features.  And by the way, aggressive stretches will emphasize vignetting, all the more reason for flats.  

For the Dubhe photo, perhaps your polar alignment was off?  

And I forgot to say, excellent images for your first effort!  

Thanks for the link regarding gain I shall have a read through it now.

I'll remember now that streaks of colour are hot pixels and that darks will help to eliminate them. I don't seem to see them with this camera but I do have them in my asi178mc.

Thanks for the compliment on my first try. I'm over the moon with how they've turned out. The more I do the better they'll get through experience and an understanding learned from research and of course you guys.

I thought I must of over exposed Dubhe making it too bright and in turn causing the spike?

1 hour ago, PeterC65 said:

I use an IMX585 based camera and you won't get any amp glow with it, but you will get hot pixels which will be reduced by using dark frames, so they are worth capturing.

Overall I think the background sky in your posted images is quite bright and you should be able to do much better. It's hard to say why this is but it could be too much gain. I use a gain of 400 and an exposure time of 4s, usually taking about 50 frames. The sky brightness could also be caused by the level of histogram stretch you are using. With 50 frames you should be able to see M51, say, quite clearly against an almost black sky, even with an 80mm refractor. The sky brightness could also be caused by glow from wispy clouds or a nearby light source, but I'd say these are less likely since all your images are similar.

I'd recommend doing some experiments with different gain and exposure settings using a specific target and comparing the results side by side. So try gains of 250, 300, 350, 400, etc and exposure times of 2s, 4s, 8s, 15s, etc take, say, 30 frame stacks for each, take a snapshot of each stack with the histogram auto stretch, then compare the results side by side. It was by doing this (on M33) that I chose the camera settings I use.

The focus may also be out a bit on some of the images. Bear in mind that the focus will need readjusting unless the kit is properly cooled. I can only get away with focussing once when I've left the kit outside cooling for 45 minutes.

 

Thanks.

I'll do some darks too.

I think the gain was between 200-250.

I do have a streetlight across the street unfortunately.

I'll have to try experimenting now I've done all the messier targets in ursa major, although leo is positioned nicely too 😆 

I'll have to try refocusing between targets and see if it helps. Should be plenty of time for the scope to cool down.

1 hour ago, Martin Meredith said:

Are you using an achromat refractor for these? If so, you can cut out some of the star bloat (eg in the last shot -- M103?) by using a filter. I started with an achromat and eventually switched to a Newt to get tighter stars.

Darks will help if you have either amp glow or hot pixels. I don't see much of either in your images. You can also do hot pixel removal without taking darks. 

Flat will help if you have dust shadows or vignetting. I see some vignetting so I'm guessing flats will help, though many find them a bit of a pain. If you do take flats, remember to take bias frames too. 

Having said that, I think the results you're getting are pretty good. Possibly you could cut back on the black point (ie darken the background) a little.

Could you say more about your equipment and the current exposure times (number of subs and total exposure) you're using?

Martin

 

Thanks.

Yes I'm using an achromatic refractor. What filter should I use for the bloating? The last photo is the ET cluster (ngc457).

I shall try using flats. Is bias the same as taking darks but with the quickest exposure possible? 

These were all using the auto histogram on the asiair plus app. I'll have to have a play with the histogram.

I have added the equipment above and the exposure times we 50 x 10 seconds for the galaxies. The stars were only single short exposures. 

What does the gain do?

48 minutes ago, Steve in Boulder said:

Flats should be a high priority.  There seems to be moderate vignetting, which flats will help with immensely.  Darks depend more on your camera's (you didn't specify which one) amp glow (aka dark current or thermal noise).  

The second to last one has elongated stars.  This could be the result of imaging near the zenith with an alt-az mount, if that's what you use. 

I'm not sure about your focus in images five through seven.  Do you use any focusing aids?

Noise is directly related to total integration time (number of subs x sub exposure time).  You haven't listed those, so it's hard to say more.  

Thanks.

I've edited the equipment above.

I will try doing some flats next time to lose the vignetting.

I've read that my camera has zero amp glow. Does that mean I don't need darks?

The second to last photo is Dubhe. It was pretty much at the zenith, it was in eq mode rather than alt az mode.

I used a bahintov mask to try and focus, maybe too long exposure time on a bright star for photo number 9.

The galaxy photos were around 50 x 10 second exposures.

Hi, 

I'm just getting started with eaa and I'm over the moon with the results I'm getting so far. 

I'm just wondering if I can enhance the images further without going down the post imaging route? 

I'm not sure what flats and darks are or how they work. Would they help? Should I do more exposures or less gain?

Any advice from experienced to a beginner would be greatly appreciated.

Here are a few photos I have taken. They seem a bit noisey/grainy? 

EDIT

Equipment used

skywatcher ao70500 and st80

Skywatcher azgti mount

Skywatcher wedge 

Zwo asi585mc 

I had exactly the same problem as you are facing! The problem for me was bad USB 3 cables. I bought the asiair plus unit and the 585mc new and both came with bad cables (they might even be USB 2 cables?). A quick way to tell is plug the USB 3 cable into a USB 2 slot. When I did this it worked. If this is the case just buy a cheap USB 3 cable off of Amazon. 

On 12/05/2023 at 09:36, Paz said:

If you want a general purpose visual observing scope but a 8-10" dobsonian is not for you then I would recommend a 4" refractor. That kind of size (e.g. 102mm f7) is easy to to handle - bigger refractors than that rapidly become serious in size/weight, and smaller apertures whilst easier to travel with due to being smaller are (imo) no easier/faster to set up if you are at home. The reason for that suggestion is it would do a bit of everything well (accepting the limitations of the aperture). My reasons for not suggesting other scopes would be...

SCT - longer focal length so slightly more specialist towards higher magnifications (but to be fair a smallish SCT would fit the vast majority of targets into the field of view), workload collimating it from time to time, longer cool down, possibly having to get into dew shields which is further workload.

Maksutov - longer focal length so more specialist towards higher magnifications, much longer cool down, possibly having to get into dew shields which is further workload. (I would add I really like Maksutovs and once set up and onto a target they are absolutely winning, and I don't like it when they get criticised, but if practicality and ease of use are key criteria then Maksutovs have some challenges compared to a refractor). 

Smaller (say 6") newtonian - workload collimating it, longer cool down (maybe not much longer?), eyepiece height / orientation challenges depending on how you mount it, a 150mm obstructed scope is more aperture than a 102mm refractor for light grasp but other than faint fuzzies where the aperture simply wins the refractor will hold up well.

I'm just a visual observer and so my comments don't take into account photography pros and cons. 

I read with interest the suggestion about electronically assisted observing from @CHR15 , I don't know much about that but that also looks a good option for something that is easy to handle and can cover a lot of ground.

I don't know much about e.a.a either. I basically type the target into goto and then press the camera button and wait for the details in the photo to come through. With each photo taken and automatically stacked the details get better and better.

On 11/05/2023 at 21:36, Marvin Jenkins said:

There is something about your whole setup and ethos that makes me recoil.

Then I think about it for about three seconds and the other non conformist side of my head says “work of pure genius”.

How do I dislike and love it all at the same time? I guess I can see the future coming and it looks good as long as I can stop thinking about ‘how it used to be done’.

Just think of the savings on EPs. Teleview are out of business.

Marv

Technology is always changing. I made the change because we have that much cloud and light pollution that I don't have much time to find and observe targets. And the fact you see much more without straining your eyes!

Hi lightfoot,

I have literally just started electronically assisted astronomy. It involves a telescope, a motorised mount, a camera and a laptop, tablet or phone.

Days are gone now of bending over to get a comfortable view in the eyepiece or straining my eyes trying to find targets, which I couldn't find most of the time as they were either to faint or because of bad light pollution.

I went for the asi air plus as the computer as it has everything set up and ready to go out of the box (the red box sitting on top of the telescope in the photo). It also connects to your phone via a wireless connection. You can sit inside and view the images as they come through if you wanted to.

My set up can easily be carried from one place to another without any hassle at all.

It is a skywatcher 70mm refractor, skywatcher azgti mount, skywatcher wedge, zwo asi air plus and a zwo asi585mc. I only observe in the back garden for now but it's possible to buy a battery that will power the rig out in the field if you want to go mobile. This is well within your budget and you will see alot more than visual astronomy, plus its also an introduction to astrophotography.

I was also in the same situation. I went for the plus in the end because its meant to be quicker loading for eaa, but also if I wanted to go more sophisticated I wouldn't need to upgrade the device.

46 minutes ago, powerlord said:

no, camera should be pointing at polaris in north. bar pointing at angle into ground to north . the azgti power port facing ground, same as bar.

So basically the bit that rotates around the bar becomes your RA, and the bit that rotates around the base becomes the DEC.

stu

 

Thanks. That's how I set mine up yesterday afternoon. I was watching a video last night about how to polar align without seeing polaris. I guess it's just another way rather than just being one way.

This maybe a bit of a silly question but as a total newbie to eq mounts, when polar aligning, is it the mount that needs to be pointing towards polaris (the threaded bar of the counterweight pointing towards it) rather than finding polaris in the eyepiece in the telescope (what I usually do before laying the telescope horizontal and doing a north level alignment in alt az mode).

I also have asiair plus which has polar alignment on it. If the camera takes photos to determine where it is pointing, obviously it won't be pointing at polaris. Is this correct? How does polar alignment work?

Following on from the diy counterweight...the official counterweight costs £35. I already had a dumbell weight so the overall cost of making my own was £10.91!

Once you've set up your rig, do you leave it fully assembled or break it down?

17 hours ago, Elp said:

Most of this is sourced via eBay, if you're lucky to have a local fastener shop around they may even give you this stuff for free depending on your relations with them. Search for large M12 washer, sort filtering to lowest price plus postage and filter to UK only to filter out the cheaper eastern prices. The washer is approx 50mm OD and 14mm ID and around 1.5-2mm thick. The flanged nuts are the serrated type so there's some metal texture to grip onto. You could add sticky backed foam onto the washers to grip the weight better but I haven't seen a need to, just make sure the OD of the washer is larger than the centre hole of the weight. If you're really picky, you could fashion a bush/nut to fit in the centre of the weights clamped to the bar to reduce their side to side movement when assembled. My all threads are 300mm long, any longer like 400mm and you may get lateral movement as there isn't enough thread engagement from the azgti to the all thread when screwed in (you can always buy longer and cut it down, but can't go the other way if it's short). Some photos of the dslr bar I use for reference:

The cost of buying potentially 2 counterweight kits to making my own makes the decision easy, especially as I already have 2×1kg dumbell weights

1 hour ago, Elp said:

Up to you if you're willing to justify the cost. Here's mine:

This is for my 6.5kg refractor load (2.25kg CWs). I've got a simpler dumbell weight only one for my dslr GTI at (1.75kg). Approx prices = M12 all thread bar (less than 5, choose what length you want or order a 1M bar and cut to length), nuts (4), washers (4), 2 off 1kg dumbell weights (3 ea), total cost (£19), and you've got more room to clamp the flat dumbell weights where you want on the bar. As mentioned the position of the weights doesn't need to be as precise on the azgti as with my gem (it's incredibly sensitive to just a mm movement in the weight position on the gem).

I never really thought of the diy way of doing it. I've already got a few dumbbell weights in the back of the wardrobe gathering dust!

What kind of washers do you use?

15 minutes ago, AstroNebulee said:

 

You can buy and try it as you'll definitely need the counterweight part and see how it fares in your setup. You may need 2 as @licho52says, I ended up buying 2. See how you go first though. You will need an M8 to M12 adapter to for the  bar. Available on Amazon and ebay. 

Lee 

There's an option to buy the bar that fits the azgti. 

25 minutes ago, licho52 said:

I have it and it works, however I bought 2 so I have 2 counterweights for my setup.

Thanks licho52, 

What's the weight of your set up?

@AstroNebulee  @Elp I was thinking of getting this https://www.rothervalleyoptics.co.uk/skywatcher-1kg-counterweight-shaft-for-star-adventurer.html

Would this be a good place to start or will the shaft be too short?