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135mm f2.8 lens test


Atreta

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Hi everybody,

finally my olympus OM mount(don't know the brand) 135mm f2.8 lens arrived :)

yesterday i could make a little test to see how it would fare. My first target was going to be m42 but the clouds rolled in, so i tried just to take some

pictures of canopus to check if infinity focus was being achieved with the fotodiox adapter.

post-37532-0-31099000-1416346419_thumb.j

It's very noisy, is there a way to  make it better? i'm yet to buy an heq5, so all i could o is 1.6s exposures.

Here is the stack, specs are:

36 x 1.6s subs @ f2.8

20 x 1.6s darks.

What can you guys and girls tell about? does it show any sign of aberration?

i'm uploading in jpeg because my connection has a terrible upload.

i think it was a good purchase for 29 dollars plus shipping.

Thanks again,

Franklin

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Those appear to be two different pictures...

They seem to be pretty close to perfect focus.

Star colours are a bit washed out which may mean you have stretched the curve a little too far at some point

I quite like the star field and I look forward to your next efforts. You will soon be smiling.

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Carina Lass,

thanks for your feedback, yeah i still need to define a routine to be taken when processing, i still just go by the feeling.

I managed to take some pictures of m42 tonight.

this is a heavily cropped stack, i know there isn't much that to begin with, but if anyone can have a go at it to improved(if i didn't ruin it already :)) it would be great.

this is about 100 x 0.6s subs @ f2.8

post-37532-0-89638700-1416369845_thumb.j

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Carina Lass,

thanks for your feedback, yeah i still need to define a routine to be taken when processing, i still just go by the feeling.

I managed to take some pictures of m42 tonight.

this is a heavily cropped stack, i know there isn't much that to begin with, but if anyone can have a go at it to improved(if i didn't ruin it already :)) it would be great.

this is about 100 x 0.6s subs @ f2.8

attachicon.gifm42 cropped2.jpg

Looking at this image I would say it has some coma.

See the star points with the fan tail.

Where from the image was this portion cropped?

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Carina Lass,

thanks for your feedback, yeah i still need to define a routine to be taken when processing, i still just go by the feeling.

I managed to take some pictures of m42 tonight.

this is a heavily cropped stack, i know there isn't much that to begin with, but if anyone can have a go at it to improved(if i didn't ruin it already :)) it would be great.

this is about 100 x 0.6s subs @ f2.8

attachicon.gifm42 cropped2.jpg

Hi,

There is not a lot that can be done with this but here it is with a quick play in PS.

Regards,

A.G

PS: This lens sufferes from a lot of CA wide open, if the focus is also off and with bad tracking the CA becomes even more obvious. I would like to see a capture with proper focusing and tracking  and then perhaps an opinion could be formed about its suitability AP, meanwhile I'd advise you to stop the lens down at least one stop while imaging.

post-28808-0-78128700-1416391984_thumb.p

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Looking at this image I would say it has some coma.

See the star points with the fan tail.

Where from the image was this portion cropped?

wxsatuser,,

It was taken from about the middle of the picture, i'll post the original picture just after stacking with no processing at all.

thank you.

Don't black clip your data. Have a look at this tutorial on levels and curves; http://www.middlehillobservatory.co.uk/articles-primers/Levels%20and%20curves.htm

Olly

Olly

thanks, gonna read it later tonight and see what i can get. 

I'm not very knowledgeable with lenses but I've been advised to stop down a little to avoid any coma. Someone please correct me if I'm wrong!

Alex, yeah i'll try stopping it down tonight and see if it gets better.

thank you for commenting

Hi,

There is not a lot that can be done with this but here it is with a quick play in PS.

Regards,

A.G

PS: This lens sufferes from a lot of CA wide open, if the focus is also off and with bad tracking the CA becomes even more obvious. I would like to see a capture with proper focusing and tracking  and then perhaps an opinion could be formed about its suitability AP, meanwhile I'd advise you to stop the lens down at least one stop while imaging.

A G,

i think all i can do is trying to stop down it, because the focus can't be moved anymore.

I have an altaz mount so i can't track yet.

thank you.

ps: here is the original picture with no processing.

post-37532-0-15335000-1416427915_thumb.j

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I notice that you have the virtuoso mount I think that can be made to track with a camera (no scope fitted but might require the L bracket) and although you will get field rotation 20-30 seconds should be do-able at 135mm FL maybe more.

Alan

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Stopping down may get rid of some of the coma.

It's the chance you take when buying and trying old lenses or in fact modern lenses.

I have bought a few old M42 lenses, the better ones being the Super Takumars.

My Canon EF 200mm f2.8 is not perfect until it's at f4.

The Sigma 105mm f2.8 Macro is very nice at f4.

I think f4 is a good place to start as it's still relatively fast, faster than most scopes.

Just purchased a mint second user Sigma 50mm f1.4, going to see how that performs.

For longer images why not make a wedge and fix the mount to it, somehow.

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I've found that 27 seconds is the max that you can do with a tracking alt/az mount.

That may be at f 10 mind you.

havent tried it with any scopes but the 8 inch

It depends on where in the sky you are imaging though. The F ratio doesn't affect the duration possible but does affect what you capture in that duration.

Olly

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I notice that you have the virtuoso mount I think that can be made to track with a camera (no scope fitted but might require the L bracket) and although you will get field rotation 20-30 seconds should be do-able at 135mm FL maybe more.

Alan

Following on from this could build a wedge for your altitude to stick the whole mount on, align the whole mount and see if that buys you slightly longer exposures. In the manual it talks about equatorial mode. A glorified barn door tracker.
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Finding this thread interesting I just bought a 135 F2.8  zeiss Jenna prime lens for a very small price, am looking for an adaptor now to make it fit my EOS, the lens has a praktica M42 mount I think, any suggestions?

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thanks everybody for the comments.

Stopping down may get rid of some of the coma.

It's the chance you take when buying and trying old lenses or in fact modern lenses.

I have bought a few old M42 lenses, the better ones being the Super Takumars.

My Canon EF 200mm f2.8 is not perfect until it's at f4.

The Sigma 105mm f2.8 Macro is very nice at f4.

I think f4 is a good place to start as it's still relatively fast, faster than most scopes.

Just purchased a mint second user Sigma 50mm f1.4, going to see how that performs.

For longer images why not make a wedge and fix the mount to it, somehow.

At first i thought about making a wedge, but as i my interest in AP is increasing i'm thinking about buying an heq5 and maybe next year a new telescope.

Near the bottom of this post is an image of a virtuoso on a wedge.
I'd try it with a camera and wide field lens first.
http://stargazerslounge.com/topic/192325-synscan-az-goto-and-a-wedge/?fromsearch=1

 Interesting thread, i'll take a look, maybe a wedge will be interesting to test before buying an eq mount

Looks very promising. What make and model is the lens please?

It's a tokina rmc 135mm f2.8, bought it at b&h photovideo.


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That's very impressive for a fixed tripod shot, you've got some nice colour coming through there and good star shapes. It will be noisy with such short exposures, every time the camera reads from the sensor it introduces some noise, which is why longer subs have a higher signal to noise ratio. Taking some dark bias frames (darks with shortest possible exposure) may help reduce read noise.

F4 will probably give better results as it puts twice as much light on the chip. Also, what stacking method are you using in DSS?

Finally, as a test it might be worth stacking just the best 50 frames or so. From my understanding of stacking the returns in image quality drop off after 30 or so subs, so you may see little difference between a stack of 50 and 150 subs. Might save you a bit of time for future attempts if this is the case.

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That's very impressive for a fixed tripod shot, you've got some nice colour coming through there and good star shapes. It will be noisy with such short exposures, every time the camera reads from the sensor it introduces some noise, which is why longer subs have a higher signal to noise ratio. Taking some dark bias frames (darks with shortest possible exposure) may help reduce read noise.

F4 will probably give better results as it puts twice as much light on the chip. Also, what stacking method are you using in DSS?

Finally, as a test it might be worth stacking just the best 50 frames or so. From my understanding of stacking the returns in image quality drop off after 30 or so subs, so you may see little difference between a stack of 50 and 150 subs. Might save you a bit of time for future attempts if this is the case.

Thank you,just got some reading through olly's  link and i found a very nice video tutorial about curves  in another topic in here. Here's the link: 

i'm stacking using the standard mode and lights, darks, etc with average. i'll try what you said about stacking the best frames.

wxsatuser

Thank you, tonight i'll give it another try :)

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