1.25" GSO Barlow 3x or 2" GSO Barlow 2x

Nordo · #1 17-07-2006, 07:16 PM

I am about to buy a GSO 10" DOB from Andrews which comes with four 1.25" EPs.
They also have the above Barlows for sale. Both have ED elements.
I want to order a Barlow when I order the scope. I would be happy with the 2x, but am a bit confused about the size (it comes with a 1.25" adapter).
Is there any advantage in having a 2" barlow over a 1.25" with your final EP being 1.25"?
Thanks

astro_nutt · #2 17-07-2006, 07:58 PM

Hi Nordo,
I think the barlow is similar to the one sold by Bintel..meaning it is a 2" barlow which takes 2' eyepieces...and by using the 1.25" adapter allows it to take 1.25 eyepieces!!!..sounds pretty good to me!!..but check with Andrews to be sure if that particular barlow DOES take both size eyepieces!!
Cheers!!

Nordo · #3 17-07-2006, 08:39 PM

The online ad says it is supplied with a 1.25"adapter.
I like the idea of a barlow giving me greater eye relief for a given power.
I've checked the Bintel site. Certainly sounds like the same. Bintel label it under their name, where Andrews have theirs under the Guan Sheng name.
Bintel's sells for $99.00. Andrew's GSO sells for $89.00.

dugnsuz (Doug) · #4 17-07-2006, 09:38 PM

The Bintel and the Andrews are the same barlow.
The 2" ED barlow allows you to use both 1.25" and 2" EPs.
You remove the 1.25" adaptor to allow the use of 2" EPs.
If you are going to only use 1.25" EPs I wouldn't go for this barlow.
I have hade one and sent it back - lots of internal reflections on bright objects like the moon and Jupiter.
Very dissapointing!!
For $99 you should maybe consider the Orion deluxe model available from Sirius Optics...
http://www.sirius-optics.com.au/barlowe_pieces.htm
The 2" Deluxe model is highly regarded by many IIS members so the 1.25" should be similar in quality.

It has internal baffles which eliminate this aberration in the cheaper barlows.
I have quickly learned that you get what you pay for - the old cliche.

Also, when choosing the EPs for your dob don't try to go for very high magnifications (over 300x) - you may find it a frustrating experience pushing a dob around at over 250X. I went for 32,25,20 and 15mm plossls with a 2x barlow. The 32mm didn't barlow very well but the others were very comfortable to observe with as the eyepiece lens is still quite large in diameter.
The 32mm was good for low power views.That range of EPs would give you a magnification range of 39x,50x,62.5x,83.3x,100x,125x,167x

Check out some of the barlow threads in this section
Cheers and good luck - you'll love the 10" dob too
Doug

Starkler (Geoff) · #5 17-07-2006, 10:07 PM

Quote:

Originally Posted by Nordo

Is there any advantage in having a 2" barlow over a 1.25" with your final EP being 1.25"?

Only if you want to barlow a 2" eyepiece. I dont think too many people do.
The thing is that a 2" barlow is a big thing to be swapping in and out, especially if swapping from a 1.25' ep and messing with adapters also.

I would also like to point you to a better barlow than the ones gso offer, which are mediocre. The Orion shorty-PLUS (not the shorty) is a good one in 1.25" format. The orion deluxe 2" is good, but I havent seen any reports on the 1.25" model.

jjjnettie (Jeanette) · #6 17-07-2006, 11:58 PM

I've got both of the barlows that you are interested in.
The 1.25" is definately the better quality of the two, but I do use the 2" barlow alot as well because I like the comfort of the 2" EP.
I'd go for the 1.25" barlow to start with, and if you feel the need you can buy a bigger one later.

ballaratdragons (Ken) · #7 18-07-2006, 12:25 AM

I also have 1.25" & 2" Barlows. I find that I use them both!

But I have 2" EP's as well, and it is nice to have a big view thru a big piece of glass.

Also, something to consider: If you get a 1.25" barlow you can only barlow 1.25" EP's. If you get a 2" Barlow you can Barlow both 1.25" & 2" EP's.

Up to you.

Nordo · #8 18-07-2006, 07:59 AM

Thanks everyone

At this stage I don't have plans for any 2" EPs. I just thought that looking through a 2" barlow with a 1.25" EP might minimise the degradation that a barlow normally gives - i.e. I'd be viewing through the centre area of the barlow elements (beginner's logic

).

At this stage I don't even know what the 4 EPs are that come with the GSO. I know the GSO web site says that a 9mm Plossl (1.25"), a SP32mm Kellner (2"), and a moonfilter are standard with the 10" dob. Funny that Andrews make no mention of the Kellner and the moon filter.

Maybe I'm better off waiting til I start using the scope with the EPs they provide, then decide what I want next. I think I was taken in by what seemed to be a good price for ED elements

.

dugnsuz (Doug) · #9 18-07-2006, 08:49 AM

Quote:

Originally Posted by Nordo

At this stage I don't even know what the 4 EPs are that come with the GSO. I know the GSO web site says that a 9mm Plossl (1.25"), a SP32mm Kellner (2"), and a moonfilter are standard with the 10" dob. Funny that Andrews make no mention of the Kellner and the moon filter.
.

Hi
The Andrews Dobs come with 4 GSO plossl EPs which are OK quality to start off with. As I said above, I find the longer focal length EPs the ones to go for due to their comfortable eye relief.
If you get in touch with Lee Andrews he may let you decide which 4 GSO plossls you want to come with the dob.
Cheers
Doug

ballaratdragons (Ken) · #10 18-07-2006, 01:50 PM

John,

It will be worth holding off on the Barlow until you see what EP's arrive with the scope.
It has happened that Andrews sometimes sends a 2" EP in the batch, but usually 4 - 1.25" EP's.

He always includes a Moon Filter, and a set of small Binoculars.

You don't really want a Kellner anyway. Plossls are more advanced and that's what he supplies.

Starkler (Geoff) · #11 18-07-2006, 06:53 PM

The Kelner is pretty awful at f5

Nordo · #12 18-07-2006, 08:36 PM

Quote:

Originally Posted by dugnsuz

Hi
If you get in touch with Lee Andrews he may let you decide which 4 GSO plossls you want to come with the dob.
Cheers
Doug

Alright Doug, you've stuck your neck out. What would you suggest for a raw beginner

(if Lee lets me select my EPs).

Nordo · #13 18-07-2006, 08:38 PM

BTW, I was going to buy Andrew's collimator (which apparently is a short Cheshire type) and make my own sight tube. Does this sound like a sensible thing to do?
Sorry, I'm a bit OT here

dugnsuz (Doug) · #14 18-07-2006, 11:54 PM

Quote:

Originally Posted by Nordo

Alright Doug, you've stuck your neck out. What would you suggest for a raw beginner

(if Lee lets me select my EPs).

I had (sold them recently after getting a Televue EP) 32mm,25mm,20mm and 15mm GSO plossls - my idea was to get a decent 2x or 3x barlow too.
The diameter of the glass you look through is large and more comfy than looking through the pinholes on 6mm and above (I had one of them too!).

So, 32/25/20/15 or 25/20/15/9...

Then, get a 1.25" 2x to double the magnifications.That way you've got a range of magnifications for most objects form deep sky to planets.

I found the 9mm the smallest eyelens I would consider comfortable - my opinion , all down to personal choice.
I think we've gone full circle here!!!

Cheers and all the best
Doug

Nordo · #15 19-07-2006, 07:52 AM

Thanks Doug
So you replaced 4 EPs with one Televue???

If I get a barlow (like a good Orion) I shouldn't need a 9mm or higher.
What's the Orion Ultrascopic FMC all about?

dugnsuz (Doug) · #16 19-07-2006, 08:25 AM

Quote:

Originally Posted by Nordo

Thanks Doug
So you replaced 4 EPs with one Televue???

If I get a barlow (like a good Orion) I shouldn't need a 9mm or higher.
What's the Orion Ultrascopic FMC all about?

Yeah, after using the TV Panoptic, the GSO plossls didn't get used too much!
That's not to say they're bad - premium televue eps are just in a different class.
Not too sure about the Orion barlow - perhaps someone else canhelp with that one.
Cheers
Doug

Nordo · #17 19-07-2006, 08:24 PM

Thanks Doug