Pleiades and Orion

[rickwayne]

Until I actually built myself an autofocuser, a Bahtinov mask was pretty much a mission-critical item for me. You get to a point, focusing by eye, where you can't really tell that moving the ring is having any effect. But the Bahtinov knows. I personally had some trouble judging when the spike was exactly centered, others don't seem to struggle with that. But any movement at all of the focuser has a visible effect on the spike location.

The other bit of advice I'd give is not to go for a really bright star, you will often see a cleaner pattern on dimmer stars. The fatter spikes from brighter stars obscure the last little bit of accuracy. A bright star is great for getting in the ballpark, then fine-tune with a dimmer one. Note that focus can vary across the field, so if you use a bright star in the center and try to fine-tune with a dim one in the corner...that way madness lies, my friend.

[Daf1983]

8 hours ago, rickwayne said:

Until I actually built myself an autofocuser, a Bahtinov mask was pretty much a mission-critical item for me. You get to a point, focusing by eye, where you can't really tell that moving the ring is having any effect. But the Bahtinov knows. I personally had some trouble judging when the spike was exactly centered, others don't seem to struggle with that. But any movement at all of the focuser has a visible effect on the spike location.

The other bit of advice I'd give is not to go for a really bright star, you will often see a cleaner pattern on dimmer stars. The fatter spikes from brighter stars obscure the last little bit of accuracy. A bright star is great for getting in the ballpark, then fine-tune with a dimmer one. Note that focus can vary across the field, so if you use a bright star in the center and try to fine-tune with a dim one in the corner...that way madness lies, my friend.

Thanks for the advice. I will definitely look into some kind of mask to aid with focusing, as I must admit, there is some degree of guessing going on with my current approach. 

I've read that Y lord is maybe more suitable for dslr lenses, as they let more light in? They also look easier to make than a bahtinov mask(don't want to be spending more money at the minute🙈)

[chanrobi]

You need a lot more total integration time especially at f5.6

[happy-kat]

Good point above re stars. Focusing on a star on a third intersection evens focus across the centre and edges of the lens.

[Daf1983]

Hello everyone. After all the advice I received on this thread, I've managed to find a couple of hours of cloudless skies to try out this lens again. This time, I took some flat and dark flat frames (not that hard after all), and used some noise reduction plug ins for gimp. I also took more care when stretching the image, checking that the noise wasn't getting to bad as I went along.

This is my new image of M45, which I think is a slight improvement on the one in the OP.

Thanks again everyone for their tips and advice🙂

[theropod]

Yes, marked improvement.

[alacant]

14 hours ago, Daf1983 said:

new image

Hi

Love it.

To lose the dslr background mush, here's an example of masking. Bring the red peak up first to match the G and B.

Cheers and HTH

Edited December 15, 2020 by alacant

[Daf1983]

Third attempt at capturing M45. Combined some more data to the one above, and took a slightly different route while processing. Finding this hobby very addictive and rewarding👍

[Daf1983]

Had (yet another🙈) go at Pleiades this week. I upped the integration time (about 150x25s light frames) and used ISO 1600 instead of ISO 800.  I also bought some step down filter rings off Aliexpress to get rid of the big diffraction spikes caused by the lens (thanks @alacantfor the suggestion). 

I have also invested in Photoshop and the Astronomy tools plug ins to help with processing. These are the final results, the first image being heavily cropped.

Thanks again everyone for their suggestions and help on this thread. I am now saving up to buy a proper mount and telescope so I can improve my images further.