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Hey, I'm having troubles getting bright images to be in crisp focus. 

I have a 12" and when I look at bright things like Jupiter or Saturn there appears to be almost a double image, like a blurry mask, that is preventing me from achieving great focus. For example, the other night I was looking at Jupiter and I could not resolve the bands clearly because of this is extra bit of light ruining the image. It's like there a thin layer of fog or cloud refracting some extra, unwanted light. I'm sure my issue is that my scope isn't collimated well, but I collimated it the other week so I'm not sure. Any thoughts? 

Below is an image of what I have been experiencing. I do not take credit for the image. It is demonstrating the hazey image I usually see. 

Thank you for any help or advice!

Picture1.png

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Hi and welcome to SGL.

WOW !!   If you’re actually visually seeing THAT much detail on Jupiter then rejoice big time......

What you’ve posted is more like super high resolution by a very experienced imager.......

 

Ed.

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2 hours ago, Seanasaurus said:

I'm sure my issue is that my scope isn't collimated well

No chance. The type of thing you describe is usually caused by water vapour. The possibilities that I would look at are:

  • Observing when it looks clear but there is actually a layer of high cloud and/or general water vapour in the atmosphere. (Judging from clear outside this will be the case on 3/7 days this week)
  • Dew forming on the eyepiece
  • Poor coatings on a cheap eyepiece
  • A low quality filter
  • Internal reflections from the side wall of an extension tube/barlow/eyepiece
  • Light scatter from the mirror edge
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Sounds like dew on the mirror to me, have seen it myself in winter.

Alan

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Thanks to everyone, 

NGC1502, it isn't my image. I just got the first image of Jupiter I found on the web and overlaid a fuzz over it to replicate what I am seeing. Usually on a good night I can just make out the main bands. If I was seeing that level of resolution, I would be over the Moon!

Riochet and Alan Potts, if it is dew forming on the mirror or eyepiece, how can I remove/prevent it? My scope is a 12" dob, I didn't think dobs were as likely to get dew issues compared to other scopes, like SCT. 

 

Thanks guys :)

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4 hours ago, Seanasaurus said:

how can I remove/prevent it?

There is a whole load of paraphernalia around electric heaters etc. that you can install on telescopes that is supposed to keep things warm enough that dew doesn't form.  I don't got down that route.  You can also buy/make a tube extension (dew shield) out of stiff material to extend the length of the tube to help stop the ingress of cold air (I find such things unbalance my Dob and I don't want to muck around with weights on the tube to compensate.  If I dew up I just give up for the night.  EP's are slightly easier - drop them into your jacket pocket and they will last a little while once you take them out to use.

Edited by JOC
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6 minutes ago, JOC said:

There is a whole load of paraphernalia around electric heaters etc. that you can install on telescopes that is supposed to keep things warm enough that dew doesn't form.  I don't got down that route.  You can also buy/make a tube extension (dew shield) out of stiff material to extend the length of the tube to help stop the ingress of cold air (I find such things unbalance my Dob and I don't want to muck around with weights on the tube to compensate.  If I dew up I just give up for the night.  EP's are slightly easier - drop them into your jacket pocket and they will last a little while once you take them out to use.

Hi. I've always wondered if using a heated dew shield will cause a blurry image due to thermals created by heat in really cold environment? It makes sense to me? The warm air will rise and distort the light coming into the objective/opening of Newt. Reflector or Refractor/SCT etc etc ?

Wes, Liverpool, UK.

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5 minutes ago, wesdon1 said:

Hi. I've always wondered if using a heated dew shield will cause a blurry image due to thermals created by heat in really cold environment? It makes sense to me? The warm air will rise and distort the light coming into the objective/opening of Newt. Reflector or Refractor/SCT etc etc ?

Wes, Liverpool, UK.

The term "dew heater" is a bit misleading. What they do is raise the temperature around the primary optic about a degree or two above the dew point so that dew cannot form on the surface of the mirror/lens. 

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5 hours ago, Seanasaurus said:

Thanks to everyone, 

NGC1502, it isn't my image. I just got the first image of Jupiter I found on the web and overlaid a fuzz over it to replicate what I am seeing. Usually on a good night I can just make out the main bands. If I was seeing that level of resolution, I would be over the Moon!

Riochet and Alan Potts, if it is dew forming on the mirror or eyepiece, how can I remove/prevent it? My scope is a 12" dob, I didn't think dobs were as likely to get dew issues compared to other scopes, like SCT. 

 

Thanks guys :)

Hello Sean and welcome to SGL.

Jupiter is very high in Oz at the moment so you should be seeing a lot of detail on Jupiter.

You say you can just make out the main bands so it sounds like something needs action.

As a first step you have to fully cool and then collimate your scope 👍

Once that is done you should see a significant improvement in the planetary views.

However Jupiter is very bright in a 12” so you may like to invest in a neutral density filter to dim the image a little - that should help to increase  contrast and help to see more detail. 

Edited by dweller25
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1 minute ago, Cornelius Varley said:

The term "dew heater" is a bit misleading. What they do is raise the temperature around the primary optic about a degree or two above the dew point so that dew cannot form on the surface of the mirror/lens. 

oh right i see? I didn't know they only slightly increase temps? I thought the awful thermals that ruin veiws when using 'scope in urban areas would be replicated on a tiny scale with Dew Heaters but obviouselty with such a small temp increase it shouldn't really happen i would assume?

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6 hours ago, Seanasaurus said:

 

NGC1502, it isn't my image. I just got the first image of Jupiter I found on the web and overlaid a fuzz over it to replicate what I am seeing. Usually on a good night I can just make out the main bands.

 

OK thanks, I get that  😁  you were just trying to replicate the “fuzz” that you saw, not the level of detail on Jupiter.....

Good advice above to sort it, cheers, Ed.

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Thanks for all this great advice!

Next clear night I will try out your suggestions!

Are there any good or recommended neutral filters, dwdeller25? I'm a bit new to the whole filter game. Side thought, would a simple Moon filter suffice?

Thanks again

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36 minutes ago, Seanasaurus said:

Thanks for all this great advice!

Next clear night I will try out your suggestions!

Are there any good or recommended neutral filters, dwdeller25? I'm a bit new to the whole filter game. Side thought, would a simple Moon filter suffice?

Thanks again

This is what I used in my 10” but also consider a variable polarizer as it’s more flexible.

D57B11D8-F355-4EC3-99F7-45AB6269B0DA.jpeg.2de4e8325d7bafce392a219a68f77702.jpeg

 

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A 12" aperture gathers quite a bit of light, and perhaps too much for the brighter objects.

Get two of these...

https://www.bintel.com.au/product/bintel-gso-polariser-1-25-inch/?v=4442e4af0916

...and combine them for a variable-polariser.  The filter acts as a dimmer for indoor-lighting, but for the telescope instead...

190022862_variablepolariser7b.jpg.0552baa0599c0ea46112c0f6e5691c96.jpg

8FJhRRM.jpg

The filter will also reduce and even eliminate those pesky flares caused by the telescope's secondary spider-vanes.

Edited by Alan64

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G'day @Seanasaurus and welcome to SGL. :hello2:

I don't know if this type --->5addf27ccac70_variablemoonfilter.jpg.e490ce031fc7badb2a139b6d8384c995.jpg of variable polarising filter is available 'down-under' 🇦🇺 / 🇳🇿

I screw one of the filters on the eyepiece holder nosepiece, and the other on the nosepiece of the eyepiece or other accessory. Then rotate either the either eyepiece holder or eyepiece or other accessory and holding the non-rotating part until I get a comfortable view. Then tighten/pinch up the thumbscrews to hold everything in place. The only downside is that it is only available in 1.25" 

FWIW - I purchased it from a well known internet auction site.

 

 Another very useful filter is the Neodymium. neodymium.jpg.3079ff2df6006c18dd7da5e81683d4cc.jpg I call it my 'Swiss-Army knife' filter.

It almost does anything and everything.

Edited by Philip R

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You can't keep a doubt about your scope's collimation. Aim it at a 2nd or 3rd mag star at very high magnification and defocus it just a little so you see one central dot and two or three rings. Defocus on each side of sharpest focus, the pattern on one side might be clearer. If the rings and dot are perfectly concentric collimation is good. At f/5 miscollimation does not forgive so be sure of that before anything else.

Edited by Ben the Ignorant
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What I did to eliminate dew forming on my primary mirror is just added 3 fans on then back of the mirror. This creates slight air flow away from the primary and has topped any dew from forming on my primary.

I'd avoid using a dew heater on the primary since that can introduce air currents and, at worst case scenario,  astigmatism due to the uneven temperature of the primary.

On the other point, that halo you describe does look like dew related dispersion.

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1 hour ago, Seanasaurus said:

@MarsG76, could you please explain your setup with the fans? This sounds like it could work for me. Thanks!

Of course... I added a plastic cut out to cover the back of the primary, and cut holes to where the fans are... this forces more air up the tube hence creating a slight breeze up, this does stop dew from forming on the primary...

as an added bonus it helps the mirror reach equilibrium temperature faster...

see image attached...

 

IMG_3125.JPG

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That's awesome, thank you very much, @MarsG76! To clarify, you had the fans blowing air at the back of the mirror, and it would go up through the tube? Air is being blown towards the mirror?

Thank you again!

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11 minutes ago, Seanasaurus said:

That's awesome, thank you very much, @MarsG76! To clarify, you had the fans blowing air at the back of the mirror, and it would go up through the tube? Air is being blown towards the mirror?

Thank you again!

Yes, toward the mirror.

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Lots of good advice here.

I have seen an image just like the one you post very occasionally with my 12 inch scope. What caused that for me was either a fogged eyepiece because it got too cold and fogged as my eye approached it and also, once, a dewed up secondary mirror but I've only had that on a very peculiar night weatherwise. Normally my primary and secondary mirrors stay clear. To stop my eyepieces getting too cold and fogging I keep them just above the outside temperature and that does the trick. A foam lined eyepiece case helps because the foam retains some warmth for some time.

An out of collimation scope does not show quite what your image pictures - if the scope is out of collimation the contrast and detail on the planet is reduced / harder to see but the hazy halo effect you show is not collimation-related I feel. It looks like classic fogging / misting of an optic to me.

 

 

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On 09/09/2019 at 06:15, NGC 1502 said:

 

Hi and welcome to SGL.

WOW !!   If you’re actually visually seeing THAT much detail on Jupiter then rejoice big time......

What you’ve posted is more like super high resolution by a very experienced imager.......

 

Ed.

Agreed!

 

I also had the same issue with my 10 inch, I left it to come into equalbrium with surrounding temperature and manged to get a good view. Though in the last two weeks, I'm not getting the best views, as Jupiter is getting away from us.

I also noted that some nights have a turbulent atmosphere where viewing planets deteriorates extremely, specially when the planet is not up at a high angle.

 

May I ask what have you used to capture this image?

 

Edit: just realized it's not your image, my bad

Edited by PlanetGazer

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This could help as it shows the different types of viewing conditions, if you do a star test, qouted from Astro Baby's website: http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

"

 

image037.gif

Collimation perfect.
Airey disk shows neat 
concentric circles.  The innermost are dark due to the telescopes central obstruction caused by the secondary mirror.
 image038-1.gif Collimation is out of adjustment – Results such as these suggest the primary mirror is not well aligned. This is simple to correct in the field by adjusting the primary mirror collimation screws. Small adjustments only are needed.
 image039.gif Atmospheric turbulence – The air around the telescope and in its line of sight is being disrupted by rising heat or by higher altitude turbulence. You cannot star test with this present.
 image041.gif Pinched Mirror – this is the classic ‘heart’ shape indicating the primary mirror has become stressed. Initially check that the collimation adjusters are not over tight.
If the problem persists you will need to remove the primary mirror cell and make sure the clips holding the mirror to the cell have not been over tightened.
Another common cause of ‘pinching’ is often over tight tube rings.
 image040.gif Tube currents – the telescope has not cooled sufficiently to the outside air temperature. Allow the telescope more time to cool down.
 image042.gif Astigmatism can be caused by poor collimation but also by poor quality optics. Secondary mirrors which are not flat either because of bad collimation or bad polishing are typical causes.
 image043.gif Usually caused by incorrect figuring of the primary mirror. This cannot be corrected by the user. It indicates faulty optics in the mirrors design or production.
 image044.gif These show typical patterns for mirrors with poor optical surfaces. This may be caused by roughness of the mirror caused by poor polishing or damage from poor cleaning. This is not correctable."

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