#1  
Old 10-07-2015, 02:10 PM
Alasdair
Registered User

Alasdair is offline
 
Join Date: Apr 2015
Location: Melbourne, Australia
Posts: 61
Finderscope for a 10" dob?

As some of you know, I have just acquired a Skywatcher 10" collapsible Dobsonian - and of course, in honour of my purchase, Melbourne skies have been resolutely overcast.

However, last night, in an effort to get some experimental viewing in between the clouds, I thought I'd have a pot-shot at Saturn. This turned out to be very difficult, not only because of the moving clouds, but because it was not far off zenith, and I had to crouch down under the finderscope (which is a straight one) to find it. This caused cricks in my legs, knees, neck, shoulders, and all other parts of my ageing anatomy. And I failed in the short times I had of getting Saturn lined up.

I'm wondering if (a) I should get another finderscope, or (b) learn some Useful Techniques to manage the one I have?

Also, I have found that the bracket-and-shoe which hold the finderscope to the OTA, and which is secured by a single screw, is not actually all that secure - I've wound a bit of tape around mine to ensure it stays in place.

It's one thing to buy a telescope; it's quite another thing, as you would all know, of learning to use it! And I'm right at the beginning here. Happy to take any advice which can be tossed in my direction (think of it in terms of tossing scraps to a dog).
Reply With Quote
  #2  
Old 10-07-2015, 02:14 PM
glend (Glen)
Registered User

glend is offline
 
Join Date: Jun 2013
Location: Lake Macquarie
Posts: 7,033
A right angle finderscope is a much better alternative on just about any scope, the straight through ones are just toys to save a few bucks.
Reply With Quote
  #3  
Old 10-07-2015, 02:21 PM
inertia8 (Australia)
Registered User

inertia8 is offline
 
Join Date: Apr 2014
Location: Melbourne, Australia
Posts: 243
Alasdair,

First question. Have you aligned the finder to center of the view in the main scope using a distant object? tree or light pole etc?

At zenith it will be a little difficult and a right-angled finder is handy, however I wouldn't be rushing out to change it over unless you have the budget. GSO ones from Bintel are $89.

You may find that adding a telrad or rigel quickfinder down the track will make it easier to aim, however you can also aim by looking down the barrel of the scope and using one of the finder alignment knobs as a reference.

Zenith is difficult still, perhaps putting in your lowest powered eyepiece and zigzag slowly across the sky. You will learn such a technique for searching the sky as you observe more and more. I'd suggest when you do get a good night to cruise the sky with the low power eyepiece for starters.
Reply With Quote
  #4  
Old 10-07-2015, 03:32 PM
zenith's Avatar
zenith (Tim)
Registered User

zenith is offline
 
Join Date: Jun 2013
Location: Melbourne
Posts: 301
Hey there,

I have a 12" collapsible dob, and did the following to improve the usability.
1) put removable cable ties around the finder to prevent it from falling onto the mirror
2) got a right angle finder scope to save my back
3) got a telrad to find things really quickly in the sky
4) made a base with wheels so I use the scope more often
5) made a shroud, improve stray light but mainly to protect the mirror from say an eyepiece being dropped onto it

Cheers
Reply With Quote
  #5  
Old 10-07-2015, 08:20 PM
Alasdair
Registered User

Alasdair is offline
 
Join Date: Apr 2015
Location: Melbourne, Australia
Posts: 61
I have indeed aligned the finderscope - as well as I could, but in fact since then I haven't had a clear night to try it out. Even without the alignment on the first night I had it I was able to find Jupiter (but given its brightness that was very easy!), and my neighbour - a very experienced amateur astronomer - helped me find and view Saturn.

However, given my travails the other night, maybe a telrad and a right-angled finderscope would be helpful.

Seems that if I'm going to be frustrated by a fiddly finderscope then I should replace it with something which will work better for me.

Thanks for all your advice, folks!
Reply With Quote
  #6  
Old 10-07-2015, 11:53 PM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,618
Quote:
Originally Posted by glend View Post
A right angle finderscope is a much better alternative on just about any scope
Hi Glen,

That's a very subjective call. It might be the case in your opinion, it isn't in mine. I have 4 dobsonians, 3 truss scopes and a tube scope. The 18" Obsession has an 8 x 50 Antares RA finder on it. The other 3 scopes all have straight through finders on them. I much prefer the straight through finders as you can get the scope aimed along the finder axis a lot better. I will admit it does help a lot being a short arse when using a straight through finder.

Quote:
Originally Posted by glend View Post
the straight through ones are just toys to save a few bucks.
That's just a ridiculous comment. When I buy astronomy equipment I don't buy "toys" and I don't choose things based on "doing it cheaper", I base my choice around "what I want to suit my observing needs". The 3 straight through finder scopes I own are manufactured by Takahashi, Stellarvue and Williams Optics. I wouldn't call them "toys", I have found them pretty useful for some serious observing over many years. Nor were any of them "cheap" and "saved a few dollars". In fact the least expensive finderscope I own is the Antares RA on the 18" Obsession.

Cheers,
John B
Reply With Quote
  #7  
Old 11-07-2015, 12:03 AM
ausastronomer (John Bambury)
Registered User

ausastronomer is offline
 
Join Date: Mar 2005
Location: Shoalhaven Heads, NSW
Posts: 2,618
Quote:
Originally Posted by Alasdair View Post
I'm wondering if (a) I should get another finderscope, or (b) learn some Useful Techniques to manage the one I have?

Hi,

I would persevere with what you have at the moment. I have been observing for a long time and have always preferred a straight through finder over a RA finder. Although a TELRAD and a RA optical finder which I have on my 18" Obsession also works pretty well.

The smaller the dob and the taller the observer the harder it is to use a straight through optical finder. I am only 5'3" so that helps me a lot in this regard. I have 2 x 10" dobs (a truss scope and a tube scope) and both have straight through finders on them. The main thing with using a straight through finder is to learn to bend your knees, get down on your haunches and look upwards, rather than trying to bend over and look through the finder with your head sideways, or upside down. Try this for a while and see if you can come to grips with it. Otherwise a RA finder and a TELRAD may be a better option for you. To be honest I find a RA finder without a TELRAD to be pretty useless as you then don't have much to align with along the scopes optical axis.

Cheers,
John B
Reply With Quote
  #8  
Old 11-07-2015, 12:10 AM
Alasdair
Registered User

Alasdair is offline
 
Join Date: Apr 2015
Location: Melbourne, Australia
Posts: 61
I appreciate that with finderscopes, as with everything else, you have to balance usefulness, quality, and price. I might be able to work with the straight through one - maybe a stool to sit on is all I need for zenith work?

Thanks again.
Reply With Quote
  #9  
Old 11-07-2015, 09:29 AM
Tinderboxsky's Avatar
Tinderboxsky (Steve)
I can see clearly now ...

Tinderboxsky is offline
 
Join Date: Feb 2012
Location: Kingston TAS
Posts: 1,031
I agree with John. I use a straight through correct image finder and have found that they can be used quite comfortably, even at the zenith if you can get your whole body well below the finder. I have positioned it on the OTA so that high altitude viewing can be done comfortably sitting down. The added bonus of sitting is that you can comfortably spend time at the finder scope searching out difficult targets. I use an adjustable Astro chair which also means I can be leaning back when viewing avoiding any neck strain. A stool is worth trying, but something with a back that you can lean on will be more comfortable.
Cheers
Steve
Reply With Quote
  #10  
Old 11-07-2015, 10:56 AM
madwayne's Avatar
madwayne (Wayne)
Registered User

madwayne is offline
 
Join Date: Jun 2007
Location: Robertson NSW
Posts: 517
How about a red dot finder. I have one on my 12" goto dob and wouldn't want anything else. I'm 6'5" and from my observing chair, yes I can sit most of the time to observe, I use both eyes. Of course being goto I only use the finder to do my two star alignment but have used it without goto for quick moon views for friends and then it is push to. Like anything in our hobby it is horses for courses and the best one is the one you use most.

Clear skies.

Wayne
Reply With Quote
  #11  
Old 11-07-2015, 02:59 PM
SkyWatch (Dean)
Registered User

SkyWatch is offline
 
Join Date: Jan 2013
Location: Adelaide
Posts: 400
I have tried all sorts: probably the best "straight-through" one was 1/2 of an old Pentax bino, because it gave a correct image. I find the reverse views confusing, and I have never warmed to a right-angle finder, mainly because it is hard to get the feel of where you are pointing. Maybe a red-dot/telrad/rigel along with a right-angle one would be best for the neck?
In any case, I just use a Rigel Quikfinder or a red-dot now. The Rigel is good because it sits up well from the scope, so is quite easy to get your head behind when the object is high up. I am a foot taller than John, so the old neck gets quite a work-out at times (and the knees too!).
Generally I find the object is nicely within the field of view even if I am running at 100x with the scope, so I don't feel the need for a magnified finder at all.

All the best,

Dean
Reply With Quote
  #12  
Old 20-07-2015, 12:21 PM
Alasdair
Registered User

Alasdair is offline
 
Join Date: Apr 2015
Location: Melbourne, Australia
Posts: 61
Well I'm happy to report that with the supplied finderscope (and some help from my neighbour) I was last night able to have a quick squiz at Saturn, M4, Omega Centauri and the Jewel Box cluster. All good! I would like some way of fastening the finderscope more securely and more "solidly" to the OTA though.

I also need to learn better how to handle the scope to give it the small nudges required to keep an object in view... nothing that practice won't cure.

The weather in Melbourne's been shocking for viewing lately, hasn't it?
Reply With Quote
  #13  
Old 20-07-2015, 05:40 PM
raymo
Registered User

raymo is offline
 
Join Date: Sep 2011
Location: margaret river, western australia
Posts: 6,070
If you get a 12" diam. thrust bearing, as used on rotating serving devices
on restaurant tables, and fit it in place of the Teflon pads, you can adjust
the freedom of azimuthal movement by adjusting the centre bolt. They cost about $30 at any bearing retailer, and installation just needs a few D.I.Y. skills.
It has always mystified me that SW designed the finder base with the open end facing down. Remove the scope retaining screw [ hold the scope in place]and drill a deep dimple in the scope base, so if the bolt becomes a bit slack the scope can't slide out of the base. Don't drill right through the base, or the screw won't hold it firmly in place.
For the record, I can't get on with RA finders either.
raymo
Reply With Quote
Reply

Bookmarks

Tags
dobsonian, finderscope

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 11:36 PM.

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