Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

What are these dots I'm seeing?

Dob Visual
  • Please log in to reply
10 replies to this topic

#1 LordNewton

LordNewton

    Mariner 2

  • -----
  • topic starter
  • Posts: 221
  • Joined: 26 Aug 2023
  • Loc: NC, USA

Posted 19 September 2023 - 05:56 AM

Last night I was observing the moon. When the moon was completely out of focus I could see these dots on the lit up area. But when the moon was in focus there was nothing and the image was clear (except for atmospheric haze).

 

The same happened when I moved the scope to Saturn and it was out of focus. Bringing it into focus and the image was clear and when it was out of focus I could see these dots. 

 

Do I need to clean some part of the optics?

Attached Thumbnails

  • 20230919_065624.jpg


#2 happylimpet

happylimpet

    Fly Me to the Moon

  • *****
  • Posts: 7,484
  • Joined: 29 Sep 2013
  • Loc: Southampton, UK

Posted 19 September 2023 - 05:58 AM

Do I need to clean some part of the optics?

Yup.


  • Barlowbill and CowTipton like this

#3 LordNewton

LordNewton

    Mariner 2

  • -----
  • topic starter
  • Posts: 221
  • Joined: 26 Aug 2023
  • Loc: NC, USA

Posted 19 September 2023 - 06:00 AM

Yup.

What is this? and where is it? primary, secondary or eyepiece?



#4 Illinois

Illinois

    Soyuz

  • *****
  • Posts: 3,694
  • Joined: 18 Dec 2006
  • Loc: Dixon, IL. Bortle 2 land in Wis.

Posted 19 September 2023 - 06:22 AM

When you see dots and turn your eyepiece and look at dots at the same time. If dots turns is eyepiece is dirty.  If dots is not turns then mirror or second mirror is dirty.  I think dots is eyepiece. 


  • Daniel Mounsey, CrazyPanda, Another_Dave and 1 other like this

#5 CrazyPanda

CrazyPanda

    Fly Me to the Moon

  • *****
  • Posts: 5,459
  • Joined: 30 Sep 2012

Posted 19 September 2023 - 06:30 AM

When you see dots and turn your eyepiece and look at dots at the same time. If dots turns is eyepiece is dirty.  If dots is not turns then mirror or second mirror is dirty.  I think dots is eyepiece. 

This is definitely the eyepiece. The pronounced diffraction around these specks and their large size relative to the field stop indicates they are on the eyepiece - most likely the field lens.

 

These would have to be huge if they were on the objective.


Edited by CrazyPanda, 19 September 2023 - 06:39 AM.

  • happylimpet likes this

#6 ngc7319_20

ngc7319_20

    Skylab

  • *****
  • Posts: 4,261
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 19 September 2023 - 06:36 AM

Which eyepiece is this?  It is somewhere near the bottom of the eyepiece. Try rotating  the eyepiece --- see if the pattern rotates with the eyepiece.  Get a magnifying glass -- hold the eyepiece up to a bright light and look in the bottom with the magnifying glass.



#7 Barlowbill

Barlowbill

    Vanguard

  • *****
  • Posts: 2,319
  • Joined: 05 Apr 2018
  • Loc: Tulsa, Oklahoma

Posted 19 September 2023 - 06:41 AM

It's alive!  It's alive!


  • happylimpet, CowTipton and norvegicus like this

#8 LordNewton

LordNewton

    Mariner 2

  • -----
  • topic starter
  • Posts: 221
  • Joined: 26 Aug 2023
  • Loc: NC, USA

Posted 19 September 2023 - 08:44 AM

Which eyepiece is this?  It is somewhere near the bottom of the eyepiece. Try rotating  the eyepiece --- see if the pattern rotates with the eyepiece.  Get a magnifying glass -- hold the eyepiece up to a bright light and look in the bottom with the magnifying glass.

This was using the 9mm Plossl. I was too tired to investigate last night.

 

I will try my other eypeice and see if I can pinpoint the issue.



#9 TayM57

TayM57

    Vanguard

  • *****
  • Posts: 2,341
  • Joined: 15 Nov 2012
  • Loc: Stellar Cartography Lab, U.S.S. Enterprise NCC 1701-D

Posted 19 September 2023 - 08:58 AM

Looks like the EP is dirty. Like a poster said, rotate the EP to see if its the EP thats dirty.

 

Dust on the primary almost never shows up like that. It's got to be the EP.


  • happylimpet likes this

#10 LordNewton

LordNewton

    Mariner 2

  • -----
  • topic starter
  • Posts: 221
  • Joined: 26 Aug 2023
  • Loc: NC, USA

Posted 20 September 2023 - 07:13 PM

So I took the eyepiece out and aimed it at a street light in the dark. Turns out it is dirty.

How do I clean it?

#11 ngc7319_20

ngc7319_20

    Skylab

  • *****
  • Posts: 4,261
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 21 September 2023 - 01:12 AM

How do I clean it?

 

Here's a good discussion of eyepiece cleaning...

https://www.televue....n=Advice&id=103


Edited by ngc7319_20, 21 September 2023 - 01:12 AM.

  • LordNewton likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics





Also tagged with one or more of these keywords: Dob, Visual



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics