Celestron Firstscope

[EnglishNightHawk]

Hello everyone, new here and hope I am posting in the right place.

I have a 76mm Celestron Firstscope which came with 20mm & 10mm Kellner eyepieces, which give me 15x or 30x magnification.

I get nice crisp views of the moon with some crater detail, and I have seen Jupiter with the Galilean moons as a bright dot with tiny specks of light. I have a cheap x3 generic Barlow lens, which will not focus with either of my eyepieces at all. 

What I really want to know is if it's worth spending the money on a High quality x2 Barlow lens, does anyone have any experience using a Barlow lens with a Firstscope? What is the best way to get more magnification out of this Telescope?

Thanks in advance for any information, it would be greatly appreciated.

[ronin]

I am not sure a more expensive barlow will help. For the reason that the scope is f/3.9 and that is fast. I would suspect that the problem is caused by this. Additionally I have no idea if parabolic or spherical but I suspect spherical.

To get anything that will work well on a scope this fast is the problem and although a barlow doubles the focal length it does however mean that the barlow needs to work on a fast scope.

The scope is not expensive and that brings in the aspect of of getting an eyepiece or barlow that is significantly more then the cost of the scope itself. Do you intend to get something else in the near future? If so then think on what and perhaps buy an eyepiece that you can use on the Firstscope then use on the next.

I would half suggest something like a 6mm plossl, would deliver 50x, however the same consideration applies - will a plossl operate at f/3.9. TV plossls are good and are reckoned to be OK to f/4, you are still a little faster and a TV plossl is I suspect something like $80 in the US and they stop at 8mm anyway.

Any chance of borrowing a plossl or two just to find out if they would perform?

That would appear the safe and sensible option.

Or borrow a barlow to try out.

I do not want to say "Go buy XYZ barlow at $100" as I half suspect getting one that works will be difficult, and I think keeping the money towards a better scope in the future may be more benificial.

[happy-kat]

Hi

Are you using the supplied eye peices or have you bought others already that you use with it?

[EnglishNightHawk]

Thanks for the fast reply's, really appreciated!

I am using the supplied 20mm & 10mm eyepieces, I am considering  Plossl eyepiece as most people say this drastically changes the quality. I understand that the supplied eyepieces aren't amazing, but they are better than I expected. The problem is the Barlow will not focus at all, and i'm wondering if it's the poor Barlow quality doing it. For instance if I get a 5mm Plossl to gain more magnification I will lose a lot of eye relief, just wondered if a decent Barlow would help me gain magnification while keeping the 10mm eye relief.

Thanks again, appreciate any more input.

[NGC 1502]

Any barlow lens, even a poor one, should at the very least come to focus.

The barlow will only produce an image when used with an eyepiece.   The barlow is inserted into the focuser, then the eyepiece is inserted into the barlow, then adjust the focuser.

Hope you sort it, Ed.

[EnglishNightHawk]

The supplied eyepieces work pretty well, albeit not as good as Plossl i'm sure. I am inserting the Barlow into the focuser and then inserting the eyepiece into the Barlow, and all I get is pure fuzz.

I plan on upgrading to a bigger Celestron Reflector telescope in the near future, so I may just invest in a decent Plossl eyepiece and Barlow which I can keep for future use anyway.

What does everyone think? Considering I will be upgrading this seems to be the best logical option.

Thanks again, very much appreciated.

[baggywrinkle]

The max theoretical magnification for 76mm is around 140, and that would be under good conditions. Often the combinations supplied as first lenses and a barlow often give powers that are too much for the OTA and hence lack of focus, it will also bring out any aberations in the mirror.

[EnglishNightHawk]

After taking everything into consideration I bought a 4mm Plossl eyepiece, which will give me 75x magnification. The supplied 10mm Kellner eyepiece gives 30x with my telescope, so theoretically the 3x Barlow would make it 90x magnification? Like you stated the max useful magnification would be around 140, so that combo should of worked but I have a feeling that Barlow is trash. This little telescope is brilliant value for money to start out with, good quality and the Dobsonian mount is sturdy. In the next week or two I should get some time to use my telescope with the new Plossl eyepiece, and I will let you know how it fares.

Thank you very much for all your replies, your knowledge has been very helpful! 

[RuneK]

Nice little scope you have there! My first scope was a 60mm "mall-scope" that came with some really bad eyepieces and a hopeless barlow. I did some investigation on the barlow, and found that the lenses was not fastened in the tube, and was possible to move by touching. I do not say that it is the problem with your 3x barlow, but I have experinced that a cheap generic barlow can have issues. The 4mm Pløssl is better than a barlow anyway because of less light dissapearing in bad lenses.

[RT65CB-SWL]

Hi 'EnglishNightHawk' and welcome to SGL.

You could try one of these: http://www.ebay.co.uk/itm/AC555-Magni-Max-1-6x-thread-on-Barlow-lens-for-photo-visual-use-/221310472031 I think I have seen them on some USA astro-dealer sites but cannot recall which. You could try www.scopestuff.com

I use one from time to time with my equipment. Extra glass in the lightpath is less photons making the trip!

[EnglishNightHawk]

The Barlow doesn't rattle or make any noise, and the lens itself seems to be in place. I figured i'd go ahead and get a Plossl for now instead of a Barlow, sacrifice some eye relief but I should get a much nicer image that way. That little Magni-Max 1.6 looks good, I am considering a Celestron Omni Barlow or as they seem to be decent quality at a good price point. 

Thanks again everyone, amazing advice!

[happy-kat]

Hope your new eye piece arrives soon as I bet you can't wait to try it on the Moon.

[EnglishNightHawk]

Looking forward to put some time in with it!