AQuestion of magnification

[BlueBird]

I have a 76mm(700mm fl) reflector. I am using a 10mm plossl eyepiece and can see Saturn at a white with yellow tinge ball with a ring around it. I can almost make out the break in the rings. The question I would ask is,
can I reasonably expect to get more magnification out of the scope?

if yes, would it be more practical to obtain a shorter fl eyepiece eg 6mm or a barlow? 2x or 3x .( I have other plossls 12.5,15,20 and 30.)

Marty.

[iceman (Mike)]

Hi Marty, welcome to IIS!

With that size reflector, you won't see a whole lot more out of Saturn, but the view could improve with the following:

1) Collimation - every newtonian owner needs to know how to do it!
2) Seeing - if the seeing is good you'll get a better view
3) Altitude - make sure you view it when it's at its highest. It's pretty low in the north for us, so wait until it's over 35deg at least.
4) Better eyepieces - while you didn't say what type of eyepiece you're using, if it's the standard ones that come with those scopes it's not likely to be the best quality.

Having said all that, it's always worth having a 2x barlow. That way you can use it with your 15mm to get increased magnification.

[BlueBird]

Thanks iceman for replying so quickly.
Collimation, thew word gives me the goosebumps. When I purchased the scope, it was because on the box it said if I wasn`t satisfied with it I could take it back for a refund. well it went back and I tried a second one. Could see the moon, but saturn... no. Then the technician in me came out. Why not. Read articles from 20 different sources as to how to collimate a newtonian. Made caps from film canisters, and adjusted and tested and adjusted and tested. got to a point where I saw 2 images of saturn in a blurry patch. Did a star test at the same time, 3 leave cloverleaf pattern.
I read the article at IIS about trouble shooter at GSO dob. astigmatism. I relieved the pressure on the mirror and packed it in so movement was almost non existent. put it back together and now its lots better. I know my daughter is impressed.

The eyepieces I purchased from astrobuysell from a person who said he won them at a star party. the 3 larger are series 500 and 10 and 12.5 have no branding but the writing is in gold lettering.

Can you suggest a decent barlow (or what to avoid) that doesn`t cost too much? I have read the list at Bintel and Andrews, and it leaves me confused.

thanks Marty,

[rmcpb (Rob)]

Welcome to IIS Marty

A bit of theory to start with. The maximum magnification from a scope on a REALLY great night is 2x the aperture in millimeters, so in your case we are looking at 150x. That said, there will only be a few of these nights a year so its not really worth buying a specialised eyepiece for such a small window of use.

With your focal length your existing lenses give a good range of magnifications with the 20mm giving 35x, 15 giving 47x, 12.5 giving 56x and the 10 giving 70x.

With my 200mm which has a maximum of 400x I spend most of my time between 130 and 200 with only rare trips to the higher magnifications. You will find your scope works well in the 70-100 range so a 2x barlow on the 12.5 would give you a good upper useful magnification at 112x. You would be able to see the rings of Saturn and get great views of the moon at this magnification.

As for a barlow, the old saying that you get what you pay for is true here. The Orion shorty barlows are great with the shorty plus as the standard one recommended.

Good luck and keep asking questions.

[StarKers]

Welcome Bluebird,

I joined this forum just under a month ago, and have learned heaps. I don't post much, but read a lot.

You're on the right track here. A great bunch of blokes. They all sound like experts to me.

Happy stargazing,
John.