Help with lens,

[Aenima]

Im hoping someone who knows about widefield and camera lenses can help me?

Rather than post again I will link it, please if you know what to look for in lenses regarding coma in particular i'd be very grateful if you could take a look at the images in the linked post.

Thank you for any help,

Regards

Aenima

[iksose7]

Hi Aenima, there doesn't appear to be a linked post?

[Aenima]

Doh!!

VERY good point iksose7 (Callum?) - must've just forgot!

Cheers for looking though dude, I will link in the other post as it has the full discussion there.

http://stargazerslounge.com/topic/190309-camera-lens-is-this-right-know-your-lenses/

Thanks for the heads up

Regards

Aenima

p.s Could you be Callum from budgetastro? if so, big fan cheers either way.

[iksose7]

Hey Aenima,

No problem just had a look through the discussion and it looks like anything i say will only be repeating what others have suggested unfortunately! I dont know anything about Nikon cameras or lens to be honest but i know that most of the Canon L series are high quality, i'm not sure if you may be able to buy a Canon to Nikon fit adapter (and buy a Canon L) or if Nikon has similar series of higher quality glass? Prime lens are also a much, much better bet.

Also, like everyone on the linked thread is saying, you have to pay a fair bit to get a decent astro lens with little coma ect. I paid around £600 for my second hand EF200L a couple months back but it was worth every penny its often compared to high quality scopes. Hope you manage to get a hold of what you are looking for!

Oh, and yes. I'm Callum from Budgetastro might i recognise your name?

[Aenima]

Awesome, Callum, thank you. Reason I asked is being v new to widefield - let alone lens based photography in general - I was hoping to ask advice. I like the budget astro page/site whole concept and a big fan of Dougs and the rest of you's pics and tutorials (not seen them all yet). If you didn't recognise any of my attempts at imaging then you might know me as Jay.

Dont worry about not remembering me as I don't really make the effort to stick out much, and try to avoid trouble - just wish it would return the favour and avoid me

Anyway, thanks for suggestions and I hope to be able to seek more of them at some point?

Regards

Aenima

[Psychobilly]

The major Camera manufactures will tend to have various ranges of lenses aimed at different market segments and at vastly different prices...

Generally you get what you pay for although occasionally you can get a budget model which punches well above its weight...

Astro targets are pretty demanding on lenses and will tend to show up the shortcomings...

Primes before zooms wherever possible and especially at the budget end...

Peter...

[iksose7]

I forgot to ask on my previous post - are you planning on shooting widefield DSOs or wide fields as in astro landscapes? (with foreground)

Your name does ring a bell! Be sure to stick out more often, we wont give you any trouble haha would be good to see your new wide field images on the page once you get the lens you are after

Any time you want any advice i would be happy to try and help you with the limited knowledge i have so far

Cheers

Callum

[Aenima]

Thank you. I'm wanting to try both to be honest, which is why the zooms appeal to me - they give flexibility to framing obects and if needed Zooming in on them. I did try my 28-100mm again last night but this time stopped the F number up (or is it down??) from fully open f5.6, to f8 and lowered ISO a few notches compensating by longer exposures and it made quite a difference. I also made sure to turn the focus ring to the end and let go of it carefully - its quite easy to turn - so it stayed where it was. I had been trying the back a bit thing, or just letting go caused it to 'settle' just short of the end. But the main thing was with the f/8 and longer exposures the stars looked round. Coma was present and it actually added to the 'donut' shape in extreme cases as the seagull 'wing' shape would kind of close on itself to make nearly a ring.

Here's what I mean:

If I had those star shapes in my telescope or camera attached to the scope it would indicate bad focus as well as coma due to the stars having dark dots in the middle. Out of focus stars are ring shaped, but with lenses i'm not sure if this is the case - the 'wings' of coma seem to give it a dark centre especially on close inspection. But pulling back the zoom and f/stop and exposing for longer reduces this effect by loads.

Now I can't complain about this result! Slight crop but taken about 66mm/ISO400 and exposed for 3 mins approx.

The coma and ring shapes dont seem to be noticeable at this f/length - I might be able to get pinpoint stars with a better lens but this certainly looks ok to my eyes

Regards

Aenima.

[iksose7]

Those stars looks much nicer at f8, the only problem there is you are loosing a lot of light gathering ability. You may be able to keep the lens at f5.6 and use an aperture mask. I have no idea how to make or use one though i'm afraid so cant help you there! I used to own a Canon 70-300mm which had the exact same problem and star shapes when wide open at f5.6 like that. I ended up selling it a few months back and putting the money towards buying my prime lens which i use for imaging DSOs.

If you are having problems with focusing or keeping focus, i recommend one of these - http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3286_Mikrofokussierer-mit-Fixierung-fuer-Tele-Objektive-bis-D---135mm.html

I got one and its great for making tiny adjustments in focus as well as holding focus all night! Also, if you want to nail focus on a DSLR, the best way i have found is to hook it up to a laptop so you can see the star you are trying to focus on a big screen, makes life soooooo much easier!

Thats a nice shot of the double cluster! I must of spent half an hour the other night in this area trying to frame the Heart and Soul nebs. I gave up in the end.

I've had a look around online and found that the Nikon 180mm f2.8 is a highly recommended astro lens. Heres a great review - http://www.astropix.com/HTML/I_ASTROP/EQ_TESTS/NIKON_180MM.HTM - Quite pricey new but i'm sure there will be some bargains flying around on Ebay

And if the Nikon 50mm f1.8 is anything like Canons version, then its a bargain astro lens. Great for constellation work

Cheers

Callum

[Aenima]

Thanks Callum, yes those stars look better - it might be picky of me but the way I judge the focus is to take a fast exposure of a star and zoom in the preview to see if its round, flared or ring shaped like unfocused telescope shows. But it doesnt seem to matter when zoomed back out again. The lens still cant quite reach sharpness on things like trees in the distance, but who wants pictures of trees anyway?

Probably going to keep it, after the last session gave me some results I really like, thats the main thing.

I appreciate the link, and suggested lens to look out for.

Regards,

Aenima

[Psychobilly]

A front aperture mask will still reduce the light and need increased exposure time.. the main advantage it offers is that if the lens doesn't produce a decent circular apeture when it is stopped down it will produce multiple diffraction spikes when you use it at anything other than wide open...

The microfocusers are very handy ... i made my own version.. but now I am using Canon bodies and lenses I can use remote manaul focus or even FWHM based AF using APT or BYEOS...

Peter...

[Aenima]

Quite a bit better when stacked 4 or 5 high.

Regards

Aenima

the dark bit is a roof.

[Psychobilly]

Have you tried the thirds point focusing method?

It will usually produce the best "average" focus over the whole frame and it allows me to use several of my lenses wide open...

Peter...

[iksose7]

Thats a nice image Aenima, shame about that roof though haha!

The microfocusers are very handy ... i made my own version.. but now I am using Canon bodies and lenses I can use remote manaul focus or even FWHM based AF using APT or BYEOS...

Peter...

Hi Peter, i usually use EOS on my laptop to get a good look at my focus star while manually focusing then lock it with the microfocuser. What do you mean by 'remote' manual focus?

[Psychobilly]

You can use the motors in the camera/lens to focus it remotely... you can do this from Eos Utils, APT and probably BYEOS and with the last two you can also do FWHM based AF on the liveview image...

Here's a thread of mine from a while back that explains the process using a 1000D and Eos Utils...

http://stargazerslounge.com/topic/116670-canon-1000d-remote-manual-focus/page__hl__+remote%20+focus#entry1154649

Some lens/body combos require the lens is left in AF other allow it to be in MF mode...

Peter...

[chiltonstar]

And if the Nikon 50mm f1.8 is anything like Canons version, then its a bargain astro lens. Great for constellation work

Cheers

Callum

I have a couple of 50mm Nikon lenses - one Series G and one older manual lens (Series E). I have a digital lens testing chart which I've used to assess resolution and flare etc on both of these lenses.The G lens is fantastically sharp (see this week's review in Amateur Photographer for example) and is very cheap and coma-free. However, mine doesn't focus to infinity when set to manual (stops just short of the infinity mark, at about 300 metres in terrestrial terms, and has to be focused in autofocus using liveview which I find a pain). The manual lens appears to have the same optical performance and does focus accurately - I set it on the infinity mark and don't need to check it. At f1.8, it gives nearly full resolution but some flare, this disappears at f4 which seems a good compromise. You need to use the mirror-up facility to avoid the clunk when the manual lens aperture opens.Chris

[Psychobilly]

Which lens test chart do you use?

Peter..

[chiltonstar]

Which lens test chart do you use?

Peter..

It's marked Stemmer Imaging - I use it 1/10, 1/20, 1/50 size etc.Chris

[Psychobilly]

Cheers Chris...

Peter..

Sent from my GT-P7300 using Tapatalk HD

[Aenima]

Have you tried the thirds point focusing method?

It will usually produce the best "average" focus over the whole frame and it allows me to use several of my lenses wide open...

Peter...

Can I ask if these focus settings are purely for auto-focus or does it change other things - sorry, very very new to the (non-scope photography) subject? Also, sorry again, but in the above mention of the lens stopping short of infinity focus in manual - how does autofocus make it go further? i mean wouldn't the lens turn as far as you want in manual mode?

Thanks,

Aenima

[Psychobilly]

Can I ask if these focus settings are purely for auto-focus or does it change other things - sorry, very very new to the (non-scope photography) subject? Also, sorry again, but if the above mention of the lens stopping short of infinity focus in manual - how does autofocus make it go further? i mean wouldn't the lens turn as far as you want in manual mode?

Thanks,

Aenima

Thirds point for both AF and MF...

Haven't a clue about the lens stopping short...

Peter...

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[Aenima]

OK, thanks. For some reason I assumed the focus modes were purely for the camera to figure out the autofocus. Otherwise, ive no idea what the settings do or how to use them, or even what difference the settings will make to the focus if they dont actually control the lens...(?)

The way the sensor gathers light? or something..?

Aenima

ps. the infinity comment was someone else but thought you might know

[chiltonstar]

Thirds point for both AF and MF...

Haven't a clue about the lens stopping short...

Peter...

Sent from my GT-P7300 using Tapatalk HD

I think the lens may operate differently in manual focus and autofocus modes. In MF, you rotate the front group of lens elements and they move out; in AF, an internal movement of a group of lenses usually occurs - hence the different behaviour in MF and AF of the lens.Chris

[Psychobilly]

I find it strange that the lens behaves differently in MF and AF especially if focus is achieved by moving different elements between MF and AF this isn't something I have come across with any of the kit I have used...

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[Aenima]

I just find it confusing (o.O), along with most other things that cameras do 9 elements in groups of ...... yeah well, point is i'm still getting the hang of it so one of those 'for dummies' explanations will work nicely.

I have found an auto focus 55-200mm version of the one I have now which together with normal daylight stuff will be a good start, and a random 135mm soligor prime lens cheap off ebay in case it does something the zooms dont (shrug) for just over a tenner anything it does will be a bonus

Thanks for the tips and explanations guys, its funny how astrophoto is said to be difficult but I have no trouble with pictures of planets or objects light years away, but when I put a lens on and take it off bulb mode POOF goes any clue I might have about how the things work.

Baby steps....

Regards

Aenima