NGC 3372 - Second Attempt

[Krypt0]

Hi All,

I was finally able to get some form of polar alignment, SCP is directly over city lights (visibly orange light) so I cant see any stars, the inbuilt Polar scope doesn't see any stars. I used a combination of my DSLR and APT to take 5m exposures at 500mm to see star arc trails and centered the target cross hairs.

I realise this isn't accurate as its the camera being centered more than the actual mount, this inaccuracy became more noticeable the further away from SCP I imaged. I still felt like I made a lot of progress from the first time I used my mount as I was able to track pretty well up to 120s with some stars slightly elongated.

Astrobin Link (https://www.astrobin.com/full/d8dw7i/0/?nc=krypt0&real=&mod=)

Carina Imaged
40 Exposure Count
90 Exposure Seconds
250 ISO


Gear
Canon EOS 5D Mk4 (Stock)
Sigma 50-500mm 4.7-6.3f @ 500mm 6.3f
NEQ6 Pro
Astrophotography Tool
Pixinsight
Stellarium

[raymo]

Good try Krypt0, A few observations and pointers if I may.
Firstly, your stars are hugely elongated; to get round stars with the polar alignment accuracy you had for this image, 90 secs was far too long, 30-40
would have been more like it.
There is a method of drift alignment that will get you accuracy as good as you want it. It is called DARV drift alignment, just google it and print out the
instructions. The first time you try it you will probably mess about for an hour or so, but it will quickly become second nature. If you mark the ground where your tripod legs sit, the alignment won't take long at all once you are familiar
with the procedure. There are other methods, but this is free and not
difficult to learn.
Most guys with DSLRs use the ISO sweet spot for their specific camera,
which in most cases is somewhere between 800 and 1600. At ISO 250
especially with your slow lens [f/6.3] you would need very long exposures
[subs] to get much colour and detail, and they would need to be guided,
not just tracked.
Thats enough to be going on with, happy snapping.
raymo

[Craig_]

Try using SharpCap Pro for your polar alignment routine. I am not sure if it can 'talk' to a DSLR (I use it with my guide camera for PA) but if it can, you may find it simplifies the process for you. It does not require you to be able to see any stars through the polar scope (although the camera must be able to detect them), and in fact it doesn't require the use of the polar scope at all. Run the alignment routine through your DSLR/lens combo (assuming SC can communicate with Canon's) and then close it and switch to your preferred acquisition software.

[Krypt0]

Hi Raymo,

Thanks a lot for the feedback!
Agree I can certainly see that, this is also just a crop of a 30MP image so when looking at this 1:1 I can certainly see the trailing.
I tried DARV during my first try with my mount and I really struggled to make this work after spending 6 hours outside, however APT has a DARV tool built in so I'll certainly try this next time. I also had some really good advice from some other members after my first night.
I've bit the bullet and ordered a PoleMaster and adapter ring from Sidereal trading in Tullamarine, VIC, so I'm hoping to take so much of the struggle of PA.

I'll certainly work on the ISO recommendations, I believe for my camera its above 800 as you say, I'll work on lower exposure times and higher ISO and higher number of images.

Thanks again!

-Adri-

[Krypt0]

Hey Craig,

Thanks for your reply!
I started the night off using SharpCap, a previous version so I could use the polar alignment tool, however it kept crashing as soon as I tried to use it, I am able to take test shots and it works with my DSLR with the ASCOM drivers, but whenever I tried to run polar alignment it kept crashing, so I ditched it.

-Adri-