First weekend imaging

[RoloFanatic]

Hey everyone,

Just wanted to share my first ever imaging session. I recently bought a small refractor and an iOptron skyguider Pro to try my hand at taking some pictures of the night sky.

On the first night all my images were really streaky which I eventually found out was because my tripod wasn't level (very annoying). On my second evening I spent a long time getting my mount level but was still getting streaks... after a lot of trouble shooting I am embarrassed to admit that I had polar aligned with the wrong star....  Some minor adjustments to my alignment and the stars were finally points with exposure well over 120 seconds! 

The first thing I decided to point my scope at was the star cluster in Hercules since it is fairly big and very bright. Overall I am really happy with the final image. This was 24 60 second exposures with dark and bias frames. Any advice on exposure times and number of frames needed would be really appreciated, I wasnt really sure what exposure lengths would be appropriate so it took a lot of trial and error (is that the normal way of doing it? idk). One thing I do need to sort before I take more images is adjusting my flattener because there is definitely some stretching at the edges.

I also tried to take some images of Bode's galaxy but unfortunately my camera ran out of battery so I only managed to get one image which was probably exposed for too long (4 mins). Even so it kind of blew me away so I thought I would share it. It's probably the coolest thing I've ever seen! GIVE ME MORE CLEAR SKIES

[Jay6879]

Wow you got 4 minutes out of a Zenithstar 73?! I have a Star Adventurer 2i (more or less the same as the Skyguider) and I opted for the Zenithstar 61 because I thought weight and focal length would an issue. Haven't tried it out yet as I'm still waiting for the field flattener to show up, backordered.

 

Your Bode's galaxy pic doesn't look too overexposed to me though. Imagine what you'd achieve with four or five hours worth of data!  I'm only a month or so into imaging as well and have much to learn still, everytime I go out I learn something new.

 

 

Edited June 1, 2021 by Jay6879

[Clarkey]

9 hours ago, RoloFanatic said:

Any advice on exposure times and number of frames needed would be really appreciated,

I think this is something you have to work out on your own set up and where you are imaging from and how well your kit performs. For RGB I typically use 3-5 minute subs but this will vary depending on the brightness of the target. I always take at least one test exposure before imaging and use this as a guide.

As for the number of subs - the more the better. It is diminishing returns, but for more DSO's I would only image one per night and get as much data as I can. It's all about improving the signal to noise ratio. Again, this will vary depending on your location, processing skills and equipment. I would suggest you experiment and see what works. The images you have are a really good starting point so you are definitely on the right track.

There is an intereting post showing the benefits of integration time here:

Testing increasing integration times (OSC, Bortle 8) - Getting Started With Imaging - Stargazers Lounge

[Grant93]

Woah! I am impressed you got 4 minutes out of a zs73! Using the same mount here on a zs61, sometimes thinking I see trails after about 90 seconds, maybe I just need more time polar aligning!

Nice images also!

[RoloFanatic]

7 hours ago, Jay6879 said:

Wow you got 4 minutes out of a Zenithstar 73?! I have a Star Adventurer 2i (more or less the same as the Skyguider) and I opted for the Zenithstar 61 because I thought weight and focal length would an issue. Haven't tried it out yet as I'm still waiting for the field flattener to show up, backordered.

 

Your Bode's galaxy pic doesn't look too overexposed to me though. Imagine what you'd achieve with four or five hours worth of data!  I'm only a month or so into imaging as well and have much to learn still, everytime I go out I learn something new.

 

 

Thanks! I was torn between the Z73 and Z61 but then I saw the Z73 on sale second hand and just went for it. I was worried about the weight as well but having tried it out now it seems to work really well! The only issue I've had is that I can't balance the load with the Z73 and guidescope so I've been using it with no guide scope and just platesolving to find my targets. I have a red dot sight coming in the post though which I think will be ideal!

I can't wait to get back out there and have another go at Bode's galaxy (this time i ll bring the spare camera battery as well!).

 

[RoloFanatic]

51 minutes ago, Clarkey said:

I think this is something you have to work out on your own set up and where you are imaging from and how well your kit performs. For RGB I typically use 3-5 minute subs but this will vary depending on the brightness of the target. I always take at least one test exposure before imaging and use this as a guide.

As for the number of subs - the more the better. It is diminishing returns, but for more DSO's I would only image one per night and get as much data as I can. It's all about improving the signal to noise ratio. Again, this will vary depending on your location, processing skills and equipment. I would suggest you experiment and see what works. The images you have are a really good starting point so you are definitely on the right track.

There is an intereting post showing the benefits of integration time here:

Testing increasing integration times (OSC, Bortle 8) - Getting Started With Imaging - Stargazers Lounge

Thanks a lot for the advice, sounds like I just need to get some more experience under the stars.

Is there any merit in using a combination of subs with different exposure lengths?

[Jay6879]

6 hours ago, RoloFanatic said:

Thanks! I was torn between the Z73 and Z61 but then I saw the Z73 on sale second hand and just went for it. I was worried about the weight as well but having tried it out now it seems to work really well! The only issue I've had is that I can't balance the load with the Z73 and guidescope so I've been using it with no guide scope and just platesolving to find my targets. I have a red dot sight coming in the post though which I think will be ideal!

I can't wait to get back out there and have another go at Bode's galaxy (this time i ll bring the spare camera battery as well!).

 

Oh boy, I haven't even had a chance to try it out and I'm already getting aperture fever for the 73. What kind of hobby is this?

[Clarkey]

9 hours ago, RoloFanatic said:

Is there any merit in using a combination of subs with different exposure lengths?

Yes in some cases. For objects with bright areas and more diffuse parts can benefit from different exposure lengths. The Orion Nebula is a prime example. However for most nebula and galaxies you would not need to.

 

3 hours ago, Jay6879 said:

What kind of hobby is this?

Expensive and addictive - trust me. 😀

[rickwayne]

Subs of different exposure lengths: Only if a single sub can't capture the dynamic range you want, which usually means blowing out stars in order to get some dim nebulosity. Although on a few targets like the Orion Nebula, there's so much dynamic range in the nebulosity itself that folks often resort to high-dynamic-range techniques.

Sub length: So long as it's about right, total integration time will have a much greater effect on the final quality than tweaking sub-exposure time. And you can judge "about right" quite easily with a DSLR's back-panel histogram. Since for most targets, the commonest pixel value is "dark sky", just look for a big peak towards the left end of the scale. If the left edge of that peak is clear of the left edge of the histogram, you're probably OK; usually it's between 1/4 and 1/3 of the range. You can also have a look at the right side, if there are some values against the very right edge then you know you're blowing out stars. That just means that it's impossible to extract color from them; not always a deal-breaker.

Jay6879, I know you were kidding but actually "aperture fever" is a disease of visual astronomers. Aperture matters much, much, much less for imaging, since we rarely approach Dawe's Limit for resolution anyway and for a given sensor size, it is the ratio of aperture to focal length, not the raw size of the objective, that determines the total integration time needed. (I think I've stated that carefully enough to avoid re-re-re-re-igniting the perennial aperture vs. f-ratio flamewar.)