Lagoon Nebula ~ NGC 6544 6553 6520 ~ Kaus Borealis ~ M28 ~ Star Cloud & Dust Lanes

[Brian W]

I enjoy faint fuzzies and dust clouds. Can anyone suggest a lens to fit on my Sony Alpha a58 that would give me better shots than my Tamron 90mm 272E? For reasons unknown the color version didn't upload. Here's a link (https://2.bp.blogspot.com/-BdsqUZt9Mrg/WZvyrmKb6FI/AAAAAAAAamU/NH1nO0nNERMmH2RTwt1fMVgrauWdqNNAwCL cBGAs/s1600/frbs%2B1.jpg)

[Atmos]

I've really enjoyed using my Sigma Art 85mm F/1.4. I've been using it at F/2.8 and it shows some aberrations but they're better by F/4.

[Brian W]

I'll take a look, thanks.

[Atmos]

http://www.astrobin.com/full/304742/0/

This is F/2.8 with a D7200. It isn't perfect out at the edges but for F/2.8 and wide field it is acceptable :)

[Brian W]

I'm new to astrophotography so forgive this newbee question: If you're getting that good a shot with an 85mm shouldn't I be close to that (barring different skills) with my 90?

[Lognic04]

Colin used much longer exposures - 180 seconds, thus reducing noise and getting more faint objects, and to further reduce the noise he stacked almost 40 frames to reduce noise further, which then allows you to stretch the data a lot more and still have it look good.

[Brian W]

Okay so if my skill set was to equal Colin's skill set I would still need either a manually tracking mount with a wedge or something like a SkyWatcher?

[Lognic04]

yup!

[Atmos]

The lens does also help, to explain.

My first 85mm was a Nikkor 85mm F/1.8G, one of my first tests with it was some time on the Crux region. Ended up just ditching all of the data as the amount of CA was unusable even at F/5.6. It wasn't overly sharp with my D7200 so the colour rendition was non-existent , stars were soft and surrounded by purple halos.

It wasn't so bad for daytime use but for astro, I ditched most of what I took with it as it just wasn't well corrected, especially in coma as well.

Logan is correct though in that even a cheap tracking mount will help. I do a lot of wide field stuff with a 10 year old HEQ5 with stepper motors. An expensive mount with a poorly corrected lens will do better than a non tracking mount due to longer exposures. It also isn't about expensive lens'. My dirt cheap 50mm F1.8D at F/4 slaughters the 5x more expensive 85mm F/1.8G at any aperture.

[Brian W]

being a pensioner this will take a while but still lots to learn and much beauty to capture with the tools I've got.

[Brian W]

The Tamron is an excellent match for my Sony Alpha a58 and the tracking mount is on the wish list. I realize that a Robber Fly in my garden can't be equated straight across to astrophotography but it does seem to work nicely so far:)Save

[JA]

It's a very nice fly Brian.

You should enter your image in to this month's IIS photo competition here.....

http://www.iceinspace.com.au/forum/showthread.php?t=159853

after all your fly has wings, which is an entry requirement/theme for this month's photo challenge.

Best
JA

[Brian W]

I just did as you suggested.