Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

sgl_2019_sp_banner.thumb.jpg.a0ff260c05b90dead5c594e9b4ee9fd0.jpg

Jon the Newb

Of course, I have another question.....collimating

Recommended Posts

So I'm a few days in to using my new telescope. I've used it every night this week so I'm feeling more and more comfortable with it. When I look at very bright objects such as Venus I understand that their brightness causes the flares I see them around. But I also get this with a lot of fairly bright stars.   And finally this morning, I got to see Jupiter for the first time. Only I couldn't see any surface details, not because of its distance,  but rather because there was a flare coming off of Jupiter as well.    I saw three of its moons, but they didn't have a flare, just the planet itself.

I'm using an 80mm refractor , ioptron 8502.   I've read that refractors be design have some "flaring" but I feel like it's happening to the extent that I can't even enjoy plants like Jupiter.   Also, I'm only viewing it on a 25 mm eyepiece, and a 10mm eyepiece.  

I  Research images of Jupiter online for 80 mm telescope they don't seem to have this glare to them.   Understand a lot of them may have used software to edit the photos, but I'm not even seen the color of the planet itself.  Just mainly red & blue light coming from the surafce.  

This is normal for money for my type of telescope?? Do I need to do this "Collimating" that I've read about?

 Sorry to have so many questions on here, but you guys of been great in all of your help, and  it's gotten me a long way from where I began!!

Jon

 

Share this post


Link to post
Share on other sites

Jon,

the earths atmosphere can make viewing the large planets an unpleasant experience.

at the moment it is low in the sky meaning there is more atmosphere for you to look through increasing chances of a poor view.

the location of the "jet stream" also affects planet viewing , if you are looking through it then Jupiter can look like someone has a hairdryer on full speed across it.

finally, the large planets have their own atmospheres and weather, it is quite possible that this will also make the view poorer.

give it a few attempts and you will have better conditions at some point, astronomy is very much a waiting game :)

 

as for you collimation question, to do a quick check you need to get a star central in your view with your high power 10 eyepiece, then turn the focus knob to defocus  the star slightly. You want to see a set of rings appear around the central point, the rings should be evenly spaced around the star.

Refractor scopes rarely need collimation in my experience:)

 

Alan

Edited by alanjgreen

Share this post


Link to post
Share on other sites

A refractor does not require collimation. This is just for reflectors. I am guessing the two eyepieces that you have are the ones that came with the telescope? It's possible that these will be fairly low quality (but can be upgraded) compared to the telescope optics. The lower the magnification (using the 25mm) the brighter the image. It might just be that your eyepiece just isn't performing very well. It also sounds like there is an amount of chromatic aberration, this is seen as blue and red egdes to the discs of objects due to the different speeds of the light spectrum travelling through the scope optics. I remember getting my 90mm refractor and the disc of Jupiter was very bright with the 25mm. very little planetary detail visible apart from the two main equatorial belts. Things improved when I bought a couple of second hand plossl eyepieces. Then it got better still when I bought a nice ortho.

Try looking for a used plossl eyepiece. You could replace the 10mm that came with the scope (if this is what you are using) or look at something like a 15mm to sit in the middle. I believe the scope comes with Kellners which aren't great.

Share this post


Link to post
Share on other sites

Collimation is most necessary for reflector telescopes where the primary and secondary mirrors need periodic adjustment. Refractor telescopes generally are well collimated when they leave the factory - and unless they are dropped etc, will usually retain their collimation throughout their life.

Your telescope is what is known as an achromatic refractor. The main, objective lens is in fact a sandwich of two types of glass with complimentary qualities called a doublet. Although this will produce very sharp views, it also has an undesirable effect known as Chromatic Aberration (C.A.) or fringing. Different coloured light comes into focus at very slightly different lengths often causing a purple-ish fringe around brighter objects. I think this may be the glare you are experiencing.

You really have two options - adapt and live with it :icon_biggrin: (the good news is that the older you get, the less the human eye notices C.A.) or try a filter. Baader Planetarium make a Fringe Killer filter which can be useful http://agenaastro.com/baader-1-25-fringe-killer-filter.html

I think I've heard a pale yellow filter can also help to reduce C.A.

Have patience, atmospheric conditions may also be the cause of your problem. Similarly the eyepieces supplied with your scope may not be the best quality.

 

 

Edited by Putaendo Patrick
spelin

Share this post


Link to post
Share on other sites

Once again, you all have helped tremeandoulsy.   It sounds like I'm on the right path. I'm going to definitely invest in some better eyepieces because I routinely hear how much of a difference that makes

 And I'll give the planets and million attempts because like you said it could just be atmospheric conditions

Thank you, thank you, thank you! 

Share this post


Link to post
Share on other sites

I am pretty certain that better eyepieces will make a difference over your Kellners. Just don't expect to go from what you are currently seeing to Hubble like images in front of your eyes! Improvements are often subtle at first but as you will learn with this hobby, even the most subtle improvements can start to feel like giant leaps. Meade make some decent plossl's as do companies like celestron and Skywatcher to name just a couple. Ebay usally has a few up for sale at any one time and you can get a bargain. If you can get one for £20 or so and treat it nicely you should be able to sell it for pretty much what you paid.

Share this post


Link to post
Share on other sites

One other suggestion I might add in regards to reducing flaring on brighter objects would be to consider using a moon filter or similar to dim the image a little  :icon_biggrin:

Share this post


Link to post
Share on other sites

I'm shopping eBay this morning to upgrade the eyepieces..  thanks for that tip.

 

and as for the moon filet, I did pick one up, and it was quite an amazing difference.  It's funny how we want more light in our pieces, but then use a filter to cut down on overly bright objects.  I love this hobby..

 

thanks!

 

jon

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By Pogo007
      Hope someone with more experience than I, which basically means anyone that has successfully collimated a Newtonian, can answer a couple of compound questions I have based on my first and only attempt at secondary collimation of my SkyWatcher Flextube 250.
      1) All three of my secondary collimation screws were extremely snug before I did anything and I was only able to comfortably turn them counter-clockwise.  Is this normal?  Do I need to loosen all three screws first before I can properly start collimation?  Should I be turning any screw beyond "snug"?
      2) Before collimating, I placed a yellow sheet inside my OTA opposite my focuser tube and I placed a red sheet between my secondary and primary.  The view this gave through my focuser tube was of a red circle surrounded by a partial yellow ring (the secondary mirror stalk blocking a portion of this yellow annulus). While independently turning each of the secondary collimation screws counter-clockwise I looked down the focuser tube (both with and without a sight tube installed) expecting to see some change in the shape of the red area (more or less circular) and/or the yellow area (less or more even thickness).  I turned the screws no more that 2 complete revolutions.  I did not perceive any appreciable difference in what I saw and I turned each screw back (clockwise) to their original tightness before working with another of the screws.   Does it make sense that I didn't perceive any change?   Should I have turned the screws more revolutions?   Should I have loosened more than one at a time?
      Very confused and looking for your help.  Thanks
    • By nuffsed81
      I have just got a second hand Astromaster 130EQ. I want to say that i have collimated scopes before without the use of a laser but in this case i have 2 questions as this is so far out i cant see what i am looking at half the time. So hopefully you can help, thank you.
      Info about the first problem:
      The secondary mirror fixing screw that hold the mirror and the collimation allen key bolts were so loose the secondary mirror had rolled facing the bottom of the OTE. In every other case the holding screw never needed touching and all i had to do were make small adjustments with an allen key, no screwdriver was needed. So this case is a whole different scale then any other collimation i have ever needed to do. You probably all know that i need to get the center of the eyepiece in line with the center of the mirror before can move on with this step. 
      Question 1
      What is the best way to do this, shall i just eye it for now? (i have seen people measuring to the center of the eyepiece and then do the same with mirror but then i still dont know if the mirror is facing me directly.)

      Info about the second problem
      Every other time i have collimated a scope the mirror and scope were very low quality and just used for practice basically. The old scopes were used to see if i wanted to go further into this hobby which i definitely do. Any how the old scopes had a flat mirror and i could find the center by placing the mirror on paper and tracing a circle template. The thing is this mirror is concaved so any template iswill have to be pushed into the vurve (i think).
      Question 2
      So how can i center the mirror without placing it face down on a piece of paper which cant be a good thing?
      Thank you. I hope i have not gone on to much, thank you for your patience in reading a long winded post.
    • By Olli
      Hi all,
      as mentioned in a previous post I have a national Geographic 76/350 compact telescope, it maybe not the best telescope in the world..but it’s at least something I can use while I save up for a good one. However I Seem to have a problem with the secondary mirror it gets easily out of place. For example when Its center I move the telescope to look at an object but it doesn’t stay in the center  and it rotates to to which side I have moved the scope. I have a feeling that this is because it’s not colimated properly ( or at all) when I got this scope as a gift the box didn’t really come with clear instructions so have been putting it off but wanted to use it now. I’m hoping it’s an easy fix. If it does need collimating I’m hoping some of you will give me some tips on how to do it. I have taken some pictures to make it clearer on what I’m trying to say. I’ve taken two photos with the scope pointing up and the seconds mirror is center (ish) and one when it’s pointed st something and the secondary mirror has moved. I’m sorry if this sounds a stupid question but need to double check.  Also apologies if the pictures aren’t clear.


    • By htj
      Hi
      I have an Intes Alter M500. I bought this telescope, as I wanted something fairly light and portable, which could still gather a respectable amount of light, and have starfields without coma or other astigmatisms. However the scope have turned out to be somewhat of a pain to collimate, and I'm starting to get rather frustrated over it.
      Unlike the Skywatchers Maks, the scope can be adjusted both front and rear. Front is the small mirror, which can be adjusted separately from the front-correcter plate (which is fixed). Similar to the Celestron schmidt-cassegrains. The rear adjusts the whole cell containing mirror, sct thread, and inner baffel tube. Getting these two to play along nicely with each other is quite a challenge.
      I've tried collimating it with the TS concentor (I emailed TS and asked if it could be used, and they thought it could), and thought I had it nailed today, but a star test this evening proved me utterly wrong. It should be mentioned that collimating this scope in the dark is a bit of trial, as it requires three tools, a flat screwdriver, a philips screwdriver, and a 2 mm hex key - the latter being very small, so I would really like something which will work in daylight. I have read through several collimation guides for newtons and schmidt-cassegrains, but have not really been able to transfer it over to the Intes.
      Does anyone have any tips or guides to how to collimate such a beast?
      On a side note, the rings that come when defocussing a star are just beutiful and so sharply defined. But I cannot get them be round .
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.