Starting with very basic resources, need advice

[astro_noob]

Hello all, apologies in advance if this is in the wrong forum!

I have been using my dobsonian for some time, and I love what I see through my eyes.
I would love to capture good images, but I have a rather limited and basic understanding of EAA. I have tried taking pictures manually, but they're always single shots, unstacked, and often contain star trailing.

At the moment, I have:

• Celestron StarSense 8" Dobsonian: it comes with a phone app that helps me locate several objects. It's very easy and quite accurate. I don't require any other software as a result.

• Canon EOS3000D camera.

• SharpCap: basic / free version.

I have got the ASCOM driver for the DSLR and had an initial run. I used some youtube videos, especially of Tiago. But, it was a pretty bland result, I'm sure I did some things wrong ...

I do not have an EQ mount so I cannot get my telescope to track objects.

What are my options? Any steps I can take?

Thank you.

[admin]

Hi,

it's a tricky setup to use for astrophotography - because the dob doesn't track the sky you are limited to relatively short exposures of just a few seconds before the stars start to trail in the image, although if you point at targets near the north celestial pole you will be able to get away with longer than for targets near the celestial equator.

The Canon camera *might* be usable with SharpCap - it can't be used directly, but there is an ASCOM driver called 'ASCOM.DSLR' that might help make the connection. Unfortunately it's not 100% reliable, so while some people use it with great success, others struggle to get it to work at all or find it crashes frequently.

To be honest, with that particular hardware setup, I'd be tempted to take multiple captures with the camera (say 20 frames in a row of your normal exposure), then try to stack them in DeepSkyStacker or similar. It's probably worth using ISO1600 or so with the camera and capturing to RAW mode if possible - both should help.

cheers,

Robin

[astro_noob]

Hi,

it's a tricky setup to use for astrophotography - because the dob doesn't track the sky you are limited to relatively short exposures of just a few seconds before the stars start to trail in the image, although if you point at targets near the north celestial pole you will be able to get away with longer than for targets near the celestial equator.

The Canon camera *might* be usable with SharpCap - it can't be used directly, but there is an ASCOM driver called 'ASCOM.DSLR' that might help make the connection. Unfortunately it's not 100% reliable, so while some people use it with great success, others struggle to get it to work at all or find it crashes frequently.

To be honest, with that particular hardware setup, I'd be tempted to take multiple captures with the camera (say 20 frames in a row of your normal exposure), then try to stack them in DeepSkyStacker or similar. It's probably worth using ISO1600 or so with the camera and capturing to RAW mode if possible - both should help.

cheers,

Robin

Thank you Robin. Yes I did install the driver, then tried gain levels from 1600 to 6400, at 1 sec exposure, got something like this, though.

[admin]

Hi,

that looks fairly promising - not sure about the 'double rectangle' edge - that would be expected perhaps if you were live stacking but not if it was a single image.

If you are seeing stars then do try the live stacking and apply a fairly strong stretch to bring out the faint detail and see what you get (https://docs.sharpcap.co.uk/4.0/#Histogram%20Tab)

cheers,

Robin

[astro_noob]

My apologies, I should've provided more details! Yes I am able to see stars clearly, even the dim ones next to the bright ones. The camera is pretty good, considering the circumstances!

And yes those double rectangles occurred during the live stacking. I'm not quite sure why though.

I will spend some time reading through that info and give it a go. Although I am aware that there are some features not available in the free version, I am hoping to get a good result - eventually

[astro_noob]

Just had an initial trial after reading the link: this is the best I could do for now. What would you suggest?
https://imgur.com/a/hcXhdyp

[oopfan]

Hi,

Where are you pointing? If it's near the celestial equator then you'll suffer the worst star drift per exposure. Try something farther north like Cassiopeia. There is a fine double star cluster that is bright. See my photo here:

viewtopic.php?t=5987&hilit=double
and here
viewtopic.php?t=3396&hilit=double

Get on the web and search for "Perseus Double Cluster". NGC 869 and NGC 884. Hopefully your Dob's software will help you locate it.

Looking at your screenshot, it appears that you have a fair amount of light pollution, so the good news is that you can aggressively shorten your exposure. Find the exposure that virtually eliminates star trails. Once you find it, then Live Stack. You will get that "rectangle effect" seen in your first photo. That will put an upper limit on the length of time you can Live Stack.

Good luck,
Brian

[astro_noob]

Hi Brian,
Those are wonderful pictures!

I was pointing at the Eta Carinae cluster/nebula in that picture. That was close to the celestial equator as it was moving pretty fast, even with a 2000 ms exposure. I live in a Bortle 6 zone.
I've attached the log files from that session. I'm sure I made a few mistakes in my settings/selection, like the gain being too high.

As for the objects being near the pole, that makes sense. Last night I experimented with 400 ms to 1000 ms exposures. I know that the Lagoon Nebula and Sagittarius Star Cluster will be up high here in Sydney. I'll try then. I'd say 400 ms seems like a good compromise between fixing star trailing and settling with enough visibility.

Good news is that the SharpCap software works very quickly with my Canon camera, thanks to the ASCOM driver. So even if I mess up the image or miss my target, at least I can reposition fairly well

[oopfan]

Hi,

Eta Carinae is at -60 declination, so you're close to the pole. I wish I could offer more help but I've got zero experience with Dobs, however, I have seen posts on this forum from owners. Try typing "Dob" into the search bar.

Astrophotography is a humbling hobby perhaps more so than golf There are two factors in play: equipment and technique. Technique develops through experimentation and in my opinion is the most important. It's like learning how to be a good driver. Putting someone with a learner's permit behind the wheel of a Ferrari is a recipe for disaster. The same is true for astrophotography. I've seen people spend untold thousands of dollars on their first kit only to be disappointed to the point of giving up. So, I recommend sticking with bright objects with your Dob. I know it is tempting to go for galaxies and nebulae but you may be disappointed. Those objects require much longer integration times than star clusters. Without a way of rotating the scope to compensate for the Earth's rotation, the object is going to move out of the camera's field of view fairly rapidly. Maybe you'll get 1 minute but in my experience that is not long enough to make a really fine image. So do what you can do with the tools you have while thinking what you can grow into.

EDIT: Robin would know, ask him if it is possible to pause Live Stack after 30 seconds, then bump the scope to its initial position and resume? Do this repeatedly until you accumulate 5 to 10 minutes of frames. It's a lot of effort but it might be the key to imaging nebulae and galaxies.

Brian

[astro_noob]

Thanks again Brian

The Eta Carinae at the time was around the celestial equator, unless I'm getting something wrong?

Anyway, tonight I looked at the Ptolemy's Cluster and Lagoon Nebula targets. They were pretty high up in the sky, I had to point my telescope almost vertically. Close to the celestial pole?

Even with 400 ms exposure and 1600 gain, I was still struggling, as the objects moved fast. SharpCap crashed a couple of times (will have to try the 64 bit version).
I can try your approach, see how it goes. I'm not fussed or frustrated about the failures, as I'm still grateful for the dob and camera working well. it's a good hobby and I'm getting to learn a lot, regardless of the results.

I've attached the results from the Ptolemy's cluster practice, for reference.