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200mm f/5 and 5x barlow - images not sharp


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Hello,

I need help with my setup:

  • telescope: Newton Skywatcher 200P f/5
  • camera: Canon EOS 50D (Magic Lantern, raw video module)
  • barlow: Antares 1.25" 5x

I have seen amazing photos with similar setups (http://stargazerslounge.com/topic/234612-jupiter-best-to-date-17th-8inch-newt-5x-barlow/http://kiehl-inter.net/mosaic.html). My images are far from that and before you say I have to focus, focus focus - I did that and A LOT (even with bahtinov mask on Jupiter!). Also I check collimation of scope before each session. Even with best focus movie frames are far from sharp (also, I checked with 25mm eye piece - not even close to sharp). These are results:

Saturn stacked, avg seeing:

post-37006-0-44378000-1422434333.png

Jupiter stacked with barlow, near perfect seeing:

post-37006-0-55344500-1422434342.jpg

Mars stacked with barlow, avg seeing:

post-37006-0-70365500-1422438840.jpg

Moon stacked with and without barlow, avg seeing:

post-37006-0-17006000-1422439057.jpg

Moon stacked without barlow, avg seeing:

post-37006-0-83177400-1422438819.jpg

Jupiter not stacked, without barlow:

post-37006-0-59881600-1422434346.jpg

Any help will be appreciated I am getting desparate here.

post-37006-0-83177400-1422438819.jpg

post-37006-0-70365500-1422438840.jpg

post-37006-0-17006000-1422439057.jpg

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The scope has a "lump" (the secondary mirror and supports) in the middle of it causing diffraction and so softening the image, the mirror edges are also a source of imaging errors (coma) and so again a reduction in image quality, the barlow will be sort of averge so adding in a small amount of errors itself and magnifing existing ones.

You might be better with a 3x not a 5x, or a better "barlow" like a TV Powermate.

For planets and moon you do not really need a fast scope - 200P f/5 - the scope itself may not be the best item for the use you are making of it.

Edited by ronin
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Hello ronin!

Thanks for response! Objects are always centered so coma should not be the issue. About diffraction - I do not understand how some people make such good images with same scope and 5x barlow, do they use smaller secondary to make the differance?

I will try to borrow 3x barlow for test but it bothers me since it is obviously possible to make great images with 5x. 

About telescope usage - I did not introduce myself properly yet :) 90% of time I do DSO. Moon and planets only 1-2x/year.

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If you used a 25 mm eyepiece and the view was not sharp there's a good chance it was seeing conditions or maybe the scope still needed to cool ? 

Scope was outside 2 hours prior to observation. Seeing was good, hardly any jetstream.

Update - I never took a good look at barlow lens now I see it may be faulty since it it deformed by sides. It is not noticable when you look through it but could that be the problem? Photos are in attachments.

post-37006-0-75175900-1422465650_thumb.j

post-37006-0-52568100-1422465674_thumb.j

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Always be wary about comparing images especially when the kit used is not exactly the same. In the quoted link, the OP lists a 5x TV powermate which costs about 4x more than an  Antares 5x Barlow (for good reason) he also lists either a modded 350D or a ASI120MC, again different kit.

You don't say what your capture settings were, but on this laptop the images look to be very noisy and the gain setting on the unstacked Jupiter looks to have been too high it is too bright + the moons do not appear to be in focus.

You also don't mention what post capture processing you have performed or how many frames / % are in the stacks.

The shot of the Moon + 5x Barlow unzoomed again looks to be slightly out of focus. The mountain in the middle of the crater can appear much tighter even with a smaller telescope and a simple webcam.

Focusing with a 5x barlow and a standard SW Crayford is always going to be difficult, check out tweaking the 200P focuser threads for info about removing slop etc.

hth,

Rich

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Your images show the typical effects of bad seeing, there is not a lot that you can do about this. Planetary imaging under bad seeing is very difficult and images usually end up soft. I assume that you allowed the scope to cool down properly before tweaking the collimation and imaging.

A.G

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If those are chips in the optics, I don't see how it could possibly help.

Russell

I know it looks like it is chipped but its not - edges are smooth, the inside is weirdly deformed. But either way, it cannot help... currently I am talking with seller about replacing.  

1) also check that your mirrors are not fogged up

2) try step down aperture with front mask

hope that helps

1) mirrors were not fogged

2) with 5x barlow, telescope is f/25 so jupiter is not very bright as is - wouldn't that make it even worse?

Always be wary about comparing images especially when the kit used is not exactly the same. In the quoted link, the OP lists a 5x TV powermate which costs about 4x more than an  Antares 5x Barlow (for good reason) he also lists either a modded 350D or a ASI120MC, again different kit.

You don't say what your capture settings were, but on this laptop the images look to be very noisy and the gain setting on the unstacked Jupiter looks to have been too high it is too bright + the moons do not appear to be in focus.

You also don't mention what post capture processing you have performed or how many frames / % are in the stacks.

The shot of the Moon + 5x Barlow unzoomed again looks to be slightly out of focus. The mountain in the middle of the crater can appear much tighter even with a smaller telescope and a simple webcam.

Focusing with a 5x barlow and a standard SW Crayford is always going to be difficult, check out tweaking the 200P focuser threads for info about removing slop etc.

hth,

Rich

I realize it is different barlow but still, if I compare images its like day and night (out of focus vs. crisp sharp)... It would be nice to borrow power mate for comparison though I'll try to get it. My Canon 50D is not modded, but can this affect sharpness so much? I expected less details but still, sharper image :)

My capture settings: Magic Lantern firmware, RAW video module with crop enabled (so I use only fraction of sensor but all the pixels, more: http://www.magiclantern.fm/forum/?topic=5441.0, cca 15fps). Unstacked jupiter images are without barlow hence they are too bright (f/5). It was just sanity check, here is another stacked version done without barlow, it looks OK to me:

post-37006-0-59866900-1422528047.jpg

Post capturing process - always cca 1500 .dng frames in Autostakkert! 2, I use 5%-10% images (depends on quality graph).

Moon shots are probably out of focus, its not recent image. Thats why yesterday I took another shot of moon with barlow after focusing with Bahtinov mask, I will provide images today after I stack them.

Thanks about focuser tip, I will take a look!

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Your images show the typical effects of bad seeing, there is not a lot that you can do about this. Planetary imaging under bad seeing is very difficult and images usually end up soft. I assume that you allowed the scope to cool down properly before tweaking the collimation and imaging.

A.G

That's probably a part of problem too but still,  e.g. on monday when I took a shoot at Jupiter it was very good - stars didnt twinkle much, Jupiter was almost totally still on DSLR live view (when seeing is bad it "dances" quite a lot). 

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I know it looks like it is chipped but its not - edges are smooth, the inside is weirdly deformed. But either way, it cannot help... currently I am talking with seller about replacing.  

1) mirrors were not fogged

2) with 5x barlow, telescope is f/25 so jupiter is not very bright as is - wouldn't that make it even worse?

I realize it is different barlow but still, if I compare images its like day and night (out of focus vs. crisp sharp)... It would be nice to borrow power mate for comparison though I'll try to get it. My Canon 50D is not modded, but can this affect sharpness so much? I expected less details but still, sharper image :)

My capture settings: Magic Lantern firmware, RAW video module with crop enabled (so I use only fraction of sensor but all the pixels, more: http://www.magiclantern.fm/forum/?topic=5441.0, cca 15fps). Unstacked jupiter images are without barlow hence they are too bright (f/5). It was just sanity check, here is another stacked version done without barlow, it looks OK to me:

attachicon.gifunnamed.jpg

Post capturing process - always cca 1500 .dng frames in Autostakkert! 2, I use 5%-10% images (depends on quality graph).

Moon shots are probably out of focus, its not recent image. Thats why yesterday I took another shot of moon with barlow after focusing with Bahtinov mask, I will provide images today after I stack them.

Thanks about focuser tip, I will take a look!

To my untutored eye that looks vastly better than the original Jupiter image, look at the difference in the moons, you have captured them as small discs not fuzzy dots.

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To my untutored eye that looks vastly better than the original Jupiter image, look at the difference in the moons, you have captured them as small discs not fuzzy dots.

Original is single frame, last one is stacked - both without barlow.

Next session do not use the barlow just to eliminate it out of the equation. I eventually ended up buying the TV 2.5X powermate as I found it superior to my other 2.5X ED barlow. The stock barlows were less than useless.

A.G

I already did that for sanity check - let me just post crucial images once again for clarity:

WITH BARLOW:

post-37006-0-55344500-1422434342.jpg
post-37006-0-70365500-1422438840.jpg
post-37006-0-44378000-1422434333.png
post-37006-0-50778600-1422534529.jpg
WITHOUT BARLOW:
post-37006-0-83177400-1422438819.jpg
post-37006-0-59866900-1422528047.jpg
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Hi,

I think the lunar image is quite nice for a single shot. You have been working on DSO most of the time from your previous posts, but lunar and planetary need different tools. Just having large aperture and a huge barlow does not guarantee a good image (I have learnt this). I cannot even use a x3 barlow unless the air is really still.

The camera you are using is great for DSO (IE long exposures, large chip etc), yet for lunar and planetary a smaller chip (or one with small pixels) as well as one that can take lots of frames in a short amount of time really are the kings of planetary imaging (IMO). That is not to say you cannot use a DSLR, its just a lot more difficult. In a lot of lunar work I do, I use an 8 inch SCT, with no barlow and I use a ZWO120MM-s (mono CMOS camera). when hooked up to my laptop I take a lot of AVI's which are in the 100 frames per second mark, which helps capture moments of good seeing. I also employ the use of an IR pass filter. This also helps cut down on distortion (and is usually used as a luminance channel in LRGB images of planets). I also changed my focuser to allow small adjustments.

Also what post processing are you doing? for instance I would take my video, run it through a pre-processor (PIPP), then stack all the good images together (increase the single / noise ratio), then sharpen the resulting TIFF in Registax (wavelet feature), then put it into Photoshop to finish it...quite a lot of work. Then again when doing DSO's, I guess you have another workflow or pathway and software to follow.

keep going though...and remember to have fun!

Regards

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Thanks for detailed description of your workflow!

Actually last 2 images are stacked in Registax And processed in wavelet (both cca 2k frames). Also I am using just part of chip (crop mode) to achieve higher video fps and use all sensors in that part of chip. But it is true I havent tried ccd or at least webcam without IR filter for comparison. Maybe that will be my next step :)

And for the record, astronomy is always fun :D

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Blazar thank you very much for tip! Yesterday I decided to try again with my guiding cam instead of DSLR (QHY5-II Mono). Well looks like a big part of the problem is DSLR, since I got quite decent shot with CCD even though seeing was not very good and transparence even worse. Images of stacked Jupiter and yesterdays setup:

post-37006-0-59060300-1422993789.jpg

post-37006-0-48422000-1422993799_thumb.j

I think I will also try other things you guys suggested (improving Crayford focuser,...)

Thank you all for help!

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