Canon 85mm F/1.8

[cspratt]

Any one using this for Milky Way shots? If so can you post a couple with details etc.?

Thanks gang.

[GPFocussed]

Any one using this for Milky Way shots? If so can you post a couple with details etc.?

Thanks gang.

If you're looking to capture the Milky Way you may want to consider a shorter lens.

[cspratt]

Thanks. I want to see what the 85 can do as I have limited sky in this area. I have a " astro program" in mind but want to see what others have done with this particular lens.

[Catanonia]

You will need to limit to under 10 second exposures with no tracking as at 85mm you will get star trails.

Hence the reason for people saying use a shorter lense, unless of course you have tracking.

[cspratt]

I planned on using 5 second exposure times 6 for total of 30 seconds for stacking. Then two additional series spaced 30 minutes apart. I can track but don't wish to do this unless really required.

[Catanonia]

Give it a go, but such short stacks might not have the light gathering ability you wish for.

Good luck.

[Adrena1in]

Hmm, with 5-second exposures you're not going to capture a great deal. At f/1.8 you'll get quite a few stars, but I doubt you'll get much Milky Wayness. Plus 85mm is too long really. I mean, take a look at my "Cygnus at 50mm" thread that I posted yesterday. There's some Milky Way in that shot, but not much really, and at 85mm the field of view is going to be even smaller.

Not sure what you mean when you say you can track, but don't really want to. Does this mean you do have an equatorial mount, but don't want to use it?

[cspratt]

Hmm, with 5-second exposures you're not going to capture a great deal. At f/1.8 you'll get quite a few stars, but I doubt you'll get much Milky Wayness. Plus 85mm is too long really. I mean, take a look at my "Cygnus at 50mm" thread that I posted yesterday. There's some Milky Way in that shot, but not much really, and at 85mm the field of view is going to be even smaller.

Not sure what you mean when you say you can track, but don't really want to. Does this mean you do have an equatorial mount, but don't want to use it?


Actually, I'm just looking for stars, rather than the Milky Way star clouds itself, hence the short exposures.

Yes, I have an equatorial mount and several telescopes.

Using the 85 F1.8 lens and my Canon 40D should give me a field of 600x900 arc minutes.

Using my Sbig CCD will give me, with the same lens, a field of about 149x197 arc minutes (B&W) which may be "do able" for what I wish to accomplish. see Mattei JAAVSO, 35, 2007, pages 1-2.

[Catanonia]

grrrr, dude at least let us know what you have in terms of kit so we can work out how to help you from the noobs that come and go.

[cspratt]

See my home page: http://www.islandnet.com/~cspratt/mypage.htm which will give you an idea of what I've done over the years.

Anyway, due to ongoing health problems I want to try a digital nova hunting program (for the AAVSO) using one of my Canon cameras. I have a Canon 10D, 30D and 40D and also an SBIG 237A CCD. I felt the 85mm might work sitting on a standard tripod.

I do have a portable GEM setup using my AP 600E Goto with various scopes from a 9.25" SCT OTA to several refractors, but these take time to setup and take down. I could, in a pinch, mount the camera on top of my Celestron 6" SCT Nexstar.

I really wanted to see what others have done with this lens (astronomically speaking) as the Canon 50mm f/1.8 I have ,and others on this page use, gives too wide a field, I feel, for suitable nova hunting. I hope to get down to magnitude 11-12. It's calulated that 50 novae appear in this galaxy every year but most are missed (see Collins, P.L., JAAVSO 7,64, 1978.)

Thanks for the comments - keep them coming.

[Adrena1in]

...as the Canon 50mm f/1.8 I have ,and others on this page use, gives too wide a field, I feel, for suitable nova hunting.

Wow, now that sounds like a fascinating pastime...I wish you every success. (There's a chap in my village who's one of the top amatuer Nova hunters in the UK. He's discovered dozens.)

[cspratt]

Friday was clear so tried the lens on my 10D ( unmodified). I made really really stupid mistake ,as the focus point as marked on the Canon 85mm F/1.8 lens isn't really at infinity. Not realizing, this I placed lens at end point of range (infinity?) and left it. I know now, that I should have shifted the focusing point a wee bit.

Bottom line ,thinking the lens was at infinity, and as it wasn't, all the shots were out of focus and useless. Last night things clouded over quickly so will have to wait and retry.