Page 4 of 6 FirstFirst ... 23456 LastLast
Results 31 to 40 of 59
Like Tree94Likes

Thread: strange stars

  1. #31
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is online now dep asst Grand Moff
    Points: 104,037, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 72.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Awards:
    Most Threads Award
    Join Date
    Jul 2011
    Location
    US
    Posts
    11,703
    Points
    104,037
    Level
    100
    Thanks
    6,094
    Thanked 29,246x 9,087 Posts
    Blog Entries
    26
    Downloads
    0
    Uploads
    0

    Default Re: strange stars



    Quote Originally Posted by Gabby76 View Post
    You do not necessarily want to heat the glass as much as keep the air in front of the lens a degree or so warmer than ambient so dew does not form.
    I agree. I almost never use a heater and its always on the shield. A heater is unnecessary on dry cold winter days. I tend to use heaters on humid cool nights in the spring and fall. Heating the OTA on a cold winter night strikes me as risking creating very strong temperature differences that would make problems much worse. Let there be plenty of time to equilibrate for the OTA and heat ONLY the dew shield is the correct approach.
    chartram, Gabby76 and vvferi like this.

  2. #32
    UlteriorModem's Avatar
    UlteriorModem is online now Gold Supporter
    Points: 48,042, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 99.6%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Awards:
    3rd Most Active Award
    Join Date
    Oct 2015
    Location
    Tallahasse Florida
    Posts
    10,905
    Points
    48,042
    Level
    100
    Thanks
    776
    Thanked 2,399x 2,153 Posts
    Blog Entries
    4
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    I am not sure how this thread go focused on dew heaters. I just casually asked if they might help with his pinched optics problem in cold weather.

    Honestly I don't think that dew heaters have anything to do with his issues
    Scopes: Orion 130mm APO Triplet, Orion 8" f3.6 astrograph Mount: Celestron CGX-L Guiding: Orion 60mm f4 scope, Starlight Loadstar, PHD2 software - Cams: Planetary: ASI120mc, DSO:Atik 383L+, SGPsoftware Processing : Regisax, Deep Sky Stacker, Star Tools, Pixinsight Assistant: One very large cat
    ~ Put your money where your mount is ~


    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

  3. #33
    not_Fritz_Argelander's Avatar
    not_Fritz_Argelander is online now dep asst Grand Moff
    Points: 104,037, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 72.0%
    Achievements:
    365 Days+ Registered Achievement!2 Posts Achievement20 Posts Achievement!750 Days+ Registered Achievement!First 1000 Experience Points
    Awards:
    Most Threads Award
    Join Date
    Jul 2011
    Location
    US
    Posts
    11,703
    Points
    104,037
    Level
    100
    Thanks
    6,094
    Thanked 29,246x 9,087 Posts
    Blog Entries
    26
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    Quote Originally Posted by UlteriorModem View Post
    I am not sure how this thread go focused on dew heaters. I just casually asked if they might help with his pinched optics problem in cold weather.

    Honestly I don't think that dew heaters have anything to do with his issues
    Honestly, I think they very well might. Thermal stresses can cause pinched optics. Also the described use of the heaters seems likely an overuse of heating perhaps to the point of abuse. One needs to rule thermal effects out before panicking about the optics being intrinsically pinched. Since this seems to be a first time observation of pinching and the thermal treatment is peculiar or even extreme thermal issues are still in play.
    Gabby76 and vvferi like this.

  4. #34
    Gabby76's Avatar
    Gabby76 is online now Moderator
    Points: 43,155, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 99.7%
    Achievements:
    2 Posts Achievement20 Posts Achievement!Gallery Achievement!Album Achievement!50 Posts Achievement!
    Awards:
    Hyperactive Geek - Silver 2rst place for Activity!
    Join Date
    Jan 2016
    Location
    BC or Slovakia
    Posts
    10,061
    Points
    43,155
    Level
    100
    Thanks
    1,782
    Thanked 3,030x 2,646 Posts
    Blog Entries
    3
    Downloads
    2
    Uploads
    0

    Default Re: strange stars

    Normally these scopes have an aluminium lens cell and has quite a different expansion/ contraction rate than the glass within.
    If the scope is trying to equalize to ambient the optics and cell are at different contraction rates and adding heat will cause one to stabalize while the other is still contracting.
    I know that is a simplified explanation but it may help visualize bit.
    Refractors: Antares 105mm f/15 (Vixen Spec), Bresser 102mm f/13, Celestron 102mm f/6.5, 2-150mm f/8, Stellarvue NHNG 80mm f/6.9, Teleskop-Service 102mm f/11, Vixen ED115S f/7.7
    Mounts: Celestron CG-5, ASGT, SLT, Manfrotto Az/Alt, Skywatcher EQ-2, Vixen SXP Binoculars: Celestron, Vixen
    Eyepieces: A-Z

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.


    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

  5. #35
    Johnny J.'s Avatar
    Johnny J. is online now SUPER GIANT
    Points: 14,171, Level: 82
    Level completed: 6%, Points required for next Level: 329
    Overall activity: 11.0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!First 1000 Experience Points
    Join Date
    May 2015
    Location
    S.D.
    Posts
    903
    Points
    14,171
    Level
    82
    Thanks
    227
    Thanked 354x 302 Posts
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    Also there are some instances of stack up tolerances during manufacturing. The ID of the lens cell may have a specification of 127.5mm ±.05mm. The optics may also have an OD grind spec of 127mm ±.01. Then there is the anodizing thickness spec. It happens some times that all these spec's are right at their limits and will and can begin to interfere due to the expansion or contraction of the different materials. Much also depends on the machine tool wear and how often the manufacturer replaces tooling. Also involved is calibration of manufacturing SPC testing equipment. All these things can add up.
    JJ
    Scopes: 20"Obsession F5 Dobsonian with ArgoNavis-ServoCat Drive & 10K DSC's. OTA's: Orion 6" F5, Meade SN6 F5, Orion 120mm F7.5 EON ED, AT 72mm F6 ED. Mounts:SW EQ-6 GT on LX850 3" Leg Tripod with pier, CG5-ASGT, Vixen SP DA drive on Celestron 2" SS Leg tripod. Eyepieces:Televue:31mm T5, 22-17-12mm T4's, 10 & 8mm Ethos, 2" 2X Powermate, 1.25" 2.5X Barlow. Baader Hyperion:21-17-13-10-8-5mm.

    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

  6. The Following User Says Thank You to Johnny J. For This Useful Post:

    vvferi (01-11-2017)

  7. #36
    wboeck's Avatar
    wboeck is offline White Dwarf
    Points: 4,773, Level: 47
    Level completed: 12%, Points required for next Level: 177
    Overall activity: 2.0%
    Achievements:
    First 1000 Experience Points365 Days+ Registered Achievement!750 Days+ Registered Achievement!1000 Days+ Registered Achievement!3 Years + Achievement
    Join Date
    Nov 2010
    Location
    Omaha
    Posts
    15
    Points
    4,773
    Level
    47
    Thanks
    0
    Thanked 5x 5 Posts
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    Thermal effects can make strange things with optics. The lens cell is typically aluminun and may be tight against the lens which is glass. The aluminum contracts at a different rate than glass so cold weather can cause the aluminum cell to squeeze the lens and cause pinching of the optics. It doesn't take much to cause this. The dew may help by keeping the aluminum cell from getting too cold and contracting too much.

  8. The Following User Says Thank You to wboeck For This Useful Post:

    vvferi (01-12-2017)

  9. #37
    vvferi's Avatar
    vvferi is offline White Dwarf
    Points: 593, Level: 11
    Level completed: 86%, Points required for next Level: 7
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!
    Join Date
    Jan 2017
    Location
    Hungary
    Posts
    20
    Points
    593
    Level
    11
    Thanks
    21
    Thanked 1 Time in 1 Post
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    I cannot answer this, the heater was on right from the beginning of the seasson, camera too. The only thing is sure, in well below zero it is a repeated issue, but I never met in positive outside temps.

  10. #38
    vvferi's Avatar
    vvferi is offline White Dwarf
    Points: 593, Level: 11
    Level completed: 86%, Points required for next Level: 7
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!
    Join Date
    Jan 2017
    Location
    Hungary
    Posts
    20
    Points
    593
    Level
    11
    Thanks
    21
    Thanked 1 Time in 1 Post
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    Quote Originally Posted by wboeck View Post
    Thermal effects can make strange things with optics. The lens cell is typically aluminun and may be tight against the lens which is glass. The aluminum contracts at a different rate than glass so cold weather can cause the aluminum cell to squeeze the lens and cause pinching of the optics. It doesn't take much to cause this. The dew may help by keeping the aluminum cell from getting too cold and contracting too much.
    Yes, I was too thinking of it just after I put the picture on. As I use the heater, it first hit the alu tube extension, after this a thin layer of air, then fallows the OTA alu wall, then some airspace again or some isolator , and finally the lens keeping rings.... You are absolutelly right, it better to put the heater a bit behind the lense plane, but in exchange it will heat the OTA, excluding the cap, a layer of air ... Thank you!

  11. #39
    vvferi's Avatar
    vvferi is offline White Dwarf
    Points: 593, Level: 11
    Level completed: 86%, Points required for next Level: 7
    Overall activity: 0%
    Achievements:
    2 Posts Achievement20 Posts Achievement!
    Join Date
    Jan 2017
    Location
    Hungary
    Posts
    20
    Points
    593
    Level
    11
    Thanks
    21
    Thanked 1 Time in 1 Post
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    Quote Originally Posted by wboeck View Post
    I meant the heater should not be placed on the dew shield. This is because the dew shield is insulated from the ota. I think it would be better to place it off of the dew shield and on the ota. It will be further from the lens but heat should still get to the glass and may work better.
    Yes, I was too thinking of it just after I put the picture on. As I use the heater, it first hit the alu tube extension, after this a thin layer of air, then fallows the OTA alu wall, then some airspace again or some isolator , and finally the lens keeping rings.... You are absolutelly right, it better to put the heater a bit behind the lense plane, but in exchange it will heat the OTA, excluding the cap, a layer of air ... Thank you!

  12. #40
    UlteriorModem's Avatar
    UlteriorModem is online now Gold Supporter
    Points: 48,042, Level: 100
    Level completed: 0%, Points required for next Level: 0
    Overall activity: 99.6%
    Achievements:
    2 Posts Achievement20 Posts Achievement!5 Threads Achievement!50 Posts Achievement!200+ Posts Achievement!
    Awards:
    3rd Most Active Award
    Join Date
    Oct 2015
    Location
    Tallahasse Florida
    Posts
    10,905
    Points
    48,042
    Level
    100
    Thanks
    776
    Thanked 2,399x 2,153 Posts
    Blog Entries
    4
    Downloads
    0
    Uploads
    0

    Default Re: strange stars

    I have always heard that the heater band should be on the dew shield equal with or just above the objective.

    You are not trying to heat the objective itself rather to have slightly warmer air than ambient inside the tube to prevent the dew from forming.

    But quite often in temps that cold a heater is not even needed due to the extremely low relative humidity. Chances are the dew point will be a dozen or so degrees below the ambient and the chances of dew or frost forming are quite low. In the morning when things start to warm up its another story.

    If I was you I would try a 'test' without the heaters on at all and see if you still have issues.
    Scopes: Orion 130mm APO Triplet, Orion 8" f3.6 astrograph Mount: Celestron CGX-L Guiding: Orion 60mm f4 scope, Starlight Loadstar, PHD2 software - Cams: Planetary: ASI120mc, DSO:Atik 383L+, SGPsoftware Processing : Regisax, Deep Sky Stacker, Star Tools, Pixinsight Assistant: One very large cat
    ~ Put your money where your mount is ~


    To view links or images in signatures your post count must be 5 or greater. You currently have 0 posts.

  13. The Following User Says Thank You to UlteriorModem For This Useful Post:

    vvferi (01-12-2017)

 

 
Page 4 of 6 FirstFirst ... 23456 LastLast

Similar Threads

  1. 10 Strange Theoretical Stars
    By Braingasim in forum Off Topic Forum
    Replies: 5
    Last Post: 10-29-2015, 08:09 AM
  2. Strange stars in images
    By ma_khan in forum Astronomy Digital Cameras Forum
    Replies: 11
    Last Post: 07-22-2015, 06:33 PM
  3. Replies: 5
    Last Post: 06-05-2015, 07:52 PM
  4. Help! Strange purple fringing on bright stars.
    By lapointejs in forum Telescope Forum
    Replies: 4
    Last Post: 02-06-2012, 03:10 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin® Version 4.2.0
Powered by vBulletin®
All times are GMT. The time now is 04:59 AM.