#1  
Old 20-04-2008, 06:12 PM
WeeGraeme
Registered User

WeeGraeme is offline
 
Join Date: Apr 2008
Location: Brisbane
Posts: 20
Finderscope Question

I think I tried following the directions on the article posted by Michael V on how to setup the finderscope, but I seem to be having a problem. I tried this afternoon, but couldn't even see the paper on a tree. I just tried to set it, looking at a star tonight without success. I'm not sure if it's a problem with me or the telescope.

The telescope is a Celestron Astromaster 130EQ. I aimed it at a star. (Actually, if I want to be 100% accurate at my level of knowledge, I aimed it at a very bright object in the sky.) It was nearly overhead and slightly to the west about half an hour ago. Near it, slightly to the south, there was another object which was less bright. I don't know how to properly describe distances in the sky, so would it be too silly of me to say that at arms length, I could fit my index finger between them, from the tip to the second joint.

That's about as close as I could get the telescope and the findersope. The telescope was aimed at the bright object. When looking through the finder scope (which is mounted on the right side of the telescope) I could see the dimmer object to the left.

Does that make any sense? I'm just trying to work out if I have a lack of understanding or if it sounds like the telescope isn't setup properly. The lack of knowledge I can work on. I'm concerned that configuring the telescope is potentially hazardous to the working of the telescope.

I'd appreciate any comments.
Reply With Quote
  #2  
Old 20-04-2008, 07:01 PM
Michael V's Avatar
Michael V
Tinkerer

Michael V is offline
 
Join Date: Mar 2008
Location: Kellyville NSW
Posts: 16
Wink Déjà vu

Hi Graeme,
I had to laugh, i had all the same problems as you did. I feel now that i have graduated to Beginner - apart from seeing Saturn's rings and jupiter's moons i have seen a nebula and a galaxy, plus the coal sack.


The target paper technique will work. I've done it with two telescopes now. Your 130mm diameter EQ is in between the two i have done it on.

So - from one beginner to another:

Forget the finder for the moment.
  • Try finding the tree before you find the paper - a fence or wall can be easier. You do this by just looking along the looking along the top and side of the telescope, and aiming it at the paper without looking through it. (Later on you will learn about laser pointers, which make this really easy)
  • Use the largest focal length lens you have to start with - possibly this will be 25mm or there abouts. - This is the walk before you run principle.
  • The short range focus of your telescope will be when the focuser is furthest out. If you can't focus on a tree or fence when your focuser is all the way out ( or nearly) you are too close. I could do it at about 25m with mine, the length of my back yard.
Once you can focus on the target paper ( made up as per the instructions in the article) http://www.iceinspace.com.au/index.p...63,477,0,0,1,0 then it will all come together.

Frustrations in those fiddly little thumb screws led me to building the mount for a red dot rifle finder scope. http://www.iceinspace.com.au/index.p...63,474,0,0,1,0. I've built two now and they work a treat.

Michael

PS - It would be worth your while reading up on Collimation - within this site and googling in the " Real world"

Last edited by Michael V; 20-04-2008 at 07:10 PM. Reason: Typos
Reply With Quote
  #3  
Old 20-04-2008, 07:13 PM
Glenhuon (Bill)
Registered User

Glenhuon is offline
 
Join Date: Apr 2007
Location: Geraldton, WA
Posts: 1,440
The tree might have been a bit too close for focus with the finder, they're set up for infinity focus. Best to try something as distant as possible during daylight. Street light, building or power pole will do OK if your in a built up area like me. Working on a fixed object is a lot easier than a drifting star. I can get mine reasonably close like that and give it a tweak on a star later to centre it.

Bill
Reply With Quote
  #4  
Old 21-04-2008, 08:54 PM
WeeGraeme
Registered User

WeeGraeme is offline
 
Join Date: Apr 2008
Location: Brisbane
Posts: 20
Quote:
Originally Posted by Michael V View Post
Hi Graeme,
I had to laugh, i had all the same problems as you did. I feel now that i have graduated to Beginner - apart from seeing Saturn's rings and jupiter's moons i have seen a nebula and a galaxy, plus the coal sack.
I've seen the moon and Saturn, but that's by aiming in the general direction and moving it around and around until I find it. The moon was relatively easy (especially last night), but it took me around 5 mins to find Saturn even when I thought I was pointing towards it.


Quote:
The target paper technique will work. I've done it with two telescopes now. Your 130mm diameter EQ is in between the two i have done it on.

So - from one beginner to another:

Forget the finder for the moment.
  • Try finding the tree before you find the paper - a fence or wall can be easier. You do this by just looking along the looking along the top and side of the telescope, and aiming it at the paper without looking through it. (Later on you will learn about laser pointers, which make this really easy)
  • Use the largest focal length lens you have to start with - possibly this will be 25mm or there abouts. - This is the walk before you run principle.
  • The short range focus of your telescope will be when the focuser is furthest out. If you can't focus on a tree or fence when your focuser is all the way out ( or nearly) you are too close. I could do it at about 25m with mine, the length of my back yard.
I thought I'd done that. I can find the paper on the tree by using the telescope, but then I don't seem to be able to adjust the finder scope to see the paper.

Quote:
Once you can focus on the target paper ( made up as per the instructions in the article) http://www.iceinspace.com.au/index.p...63,477,0,0,1,0 then it will all come together.

Frustrations in those fiddly little thumb screws led me to building the mount for a red dot rifle finder scope. http://www.iceinspace.com.au/index.p...63,474,0,0,1,0. I've built two now and they work a treat.

Michael

PS - It would be worth your while reading up on Collimation - within this site and googling in the " Real world"
I'll try again and see how I go.
Reply With Quote
  #5  
Old 21-04-2008, 08:55 PM
WeeGraeme
Registered User

WeeGraeme is offline
 
Join Date: Apr 2008
Location: Brisbane
Posts: 20
Quote:
Originally Posted by Glenhuon View Post
The tree might have been a bit too close for focus with the finder, they're set up for infinity focus. Best to try something as distant as possible during daylight. Street light, building or power pole will do OK if your in a built up area like me. Working on a fixed object is a lot easier than a drifting star. I can get mine reasonably close like that and give it a tweak on a star later to centre it.

Bill
I didn't measure the distance, but I'd say it'd be between 30 and 40 metres away. Is that ok?
Reply With Quote
  #6  
Old 21-04-2008, 09:38 PM
erick's Avatar
erick (Eric)
Starcatcher

erick is offline
 
Join Date: Dec 2006
Location: Gerringong
Posts: 8,532
Quote:
Originally Posted by WeeGraeme View Post

..... but then I don't seem to be able to adjust the finder scope to see the paper.

I take it you are saying that you cannot get the piece of paper into the field of view of the finderscope. Better stand back for a minute and have a good look at the finderscope. I don't know the style, but, is it properly mounted in the bracket? Some push into place on a rubber O-ring - is that in place properly? Is the bracket properly mounted? Where it connects to the scope, are the screws tight? The base hasn't obviously moved? Give it a push and shove and check it is firm? A problem with the mounting can be why you cannot get the paper in the field of view within the range of the adjustment screws.
Reply With Quote
  #7  
Old 21-04-2008, 10:53 PM
Michael V's Avatar
Michael V
Tinkerer

Michael V is offline
 
Join Date: Mar 2008
Location: Kellyville NSW
Posts: 16
Keep Trying

Hey little bloke,
30- 40 m should be alright, try to focus on the tree then the paper first. Again, try with the least magnification lenses, then work up from there. Your finder scope also has ability t focus, even the cheap ones.

Saturn is a planet, at the moment easily found in Aus. I fooled around like you did, for ages, and cricked my neck. It puts beginners off and that is why perfectly good (eBay) telescopes end up in the garage for years. But once i worked out the alignment it was a snack.
And - what erick says, smack it around a bit and use the common sense external line up techniques before the optics.

Michael
Reply With Quote
  #8  
Old 23-04-2008, 04:36 PM
WeeGraeme
Registered User

WeeGraeme is offline
 
Join Date: Apr 2008
Location: Brisbane
Posts: 20
Hi, All.

I'm still having problems aligning this.

I can find the paper in the telescope, but no matter how far I adjust the finderscope, I can't get it to line up.

Maybe I need to describe the finderscope on the Celestron so I know we're on the same wavelength. The finderscope is a moulded plastic thing, permanently attached to the open end of the telescope. It's about 4 or 5 cm long. There is a perspex disc at the front and another at the rear. Each has a circle approx 15mm in diameter and a "dot" in the middle. When I switch the scope on, an LED makes the dots appear red.

My understanding is that I need to be able to line up the object I want to see with the LED and its reflection. There are two adjusting screws which are approx 120 degrees apart and move the rear disc. The closest I can get is just inside the border of the circle.

Does that make any sense to anyone?
Reply With Quote
  #9  
Old 23-04-2008, 07:23 PM
Michael V's Avatar
Michael V
Tinkerer

Michael V is offline
 
Join Date: Mar 2008
Location: Kellyville NSW
Posts: 16
Unhappy Bent finder mount?

Hi Graeme,
I don't know this type of finder, i hope someone else does.

Assuming you have the main scope focused on the target paper ("main" target) a reasonable distance away then you should be able to adjust the finder with whatever adjustment it has to the "finder" mark on the paper. I can only guess that something on your finder is bent, and that's why you can't adjust it correctly. Maybe there is a way of shimming the mount to give you more adjusting space.

Hopefully someone else is familiar with your type of finder and can advise.

Michael
Reply With Quote
  #10  
Old 25-04-2008, 08:41 AM
Michael V's Avatar
Michael V
Tinkerer

Michael V is offline
 
Join Date: Mar 2008
Location: Kellyville NSW
Posts: 16
Another Angle?

Hi Graeme,
I don't know why i woke up thinking about this, but i did. I had another thought.

Maybe your finderscope mount is fine. If your primary mirror (Astro lingo for the big one at the back) is grossly out of alignment, (could be with a new telescope bought from a non astro suppliier, or be dislodged in transport ) then it will be gathering light from somewhere not parallel with the tube itself. This will make your finder scope difficult or possibly impossible to line up.

Read up on "collimation". There are great articles on Ice in Space, but before i discovered IIS i found great comfort in the attached article. It is a good beginner's read:

http://astronomy.concreteairship.com....htm#alignment

I discovered simply with a plastic milk bottle top with a hole in the middle in lieu of the film canister described on the link that my eBay scope was significantly out of alignment. It was probably never collimated in the first place. I was able to make great improvements in "seeing" just by adjusting by the hole in the plastic cap method. I later splurged out on a laser collimator.

Check it out with this basic method first!

Michael

Last edited by Michael V; 25-04-2008 at 08:44 AM. Reason: typo
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 12:05 AM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Testar
Advertisement
Bintel
Advertisement