To 2" or not to 2"

[GazzMeister]

Good evening everyone

I finally bit the bullet and bought a 10" Bintel dob. NOW, my troubles have been expanded:eyepop:. My (brilliant) scope came with three eyepieces, one 2" and one 1-1/4". My question to your collective excellence is, which way should I go? I'm really keen to get an OIII filter and also some other coloured filters but I can't afford to buy two of each (unless i win lotto tonight!). Are there any advantages or disadvantages between the two? The 2" seem to cost more but I presume that the extra cost is for the extra glass.

Any help or enlightenment on this conundrum will be much appreciated.

Gareth

[taminga16]

Gareth, A 2" filter will screw into the base of your 2" to 1.25" adapter, a 2" barlow and 2" EP's.
Regards Greg

[GazzMeister]

Cool, thanks Greg. Now I just need to know if the 2" is worth the extra cash...

[GazzMeister]

I just took the adapter out and saw what you're talking about. I really should have checked that out before I posted a foolish remark:whistle:.

[taminga16]

Gareth, It really is a matter of where you see yourself going with EP's, be mindful that coloured filters are generally used for planetary viewing and that wider FOV's provided by 2" EP's might not be necessary for same. A 2" nebula specific filter would be a good option that would allow use across your EP range. A 2" ND filter for luna viewing for the same reasons.

Regards Greg.

P.S. coloured filters will highlight some planetary features but I would suggest that you try viewing with them before purchase, they might end up taking -up space in your gear box that could be filled with other stuff.

[ballaratdragons]

Gareth,

My only suggestion is that you learn to count!!! :P

:lol:

[taminga16]

I saw it as a genuine question and not foolish at all. In fact it probably seant dozens of us rushing to our gear boxes.
Greg.

[Tamtarn]

Gareth. Just be aware that you may need to insert a spacer between the bottom of the adapter and the filter as some 1.25" eyepieces may hit the filter. - We need to use a spacer when using Pentax XW's otherwise the bottom of the ep would hit the 2" filter.

David

[erick]

I was thinking exactly the same, Gareth, after using my brand new 2" NPB filter with the Bintel supplied 15mm plossl last night. I could see that the end of the eyepiece would certainly come too close to the filter surface for comfort, so I made sure I raised it far enough out of the adapter and nipped it up tightly before I screwed in the filter.

[Tamtarn]

Gareth & Eric

If you buy a cheap 2" colour filter on ebay and then remove the filter and use the ring this will serve as a spacer.

David

[GazzMeister]

Thanks for all the replies people. I'm thinking that long term i'll be more into DSOs than planetary observation, so i'm leaning towards the 2".

Oh, and Ken, i know it's a typo, God help us if they start making 3" eyepieces,. I'll never make any sense:P

[janoskiss]

They do make 3 and 4" EPs. hehe. But there is no advantage to 2" over 1.25" until the field stop exceeds 27mm, i.e. it no longer fits in a 1.25" barrel. That means that 1.25" is fine for super wides (65 degree FOV) up to about 24mm or ultra wides (80-deg FOV) up to about 20mm.

Where a 2" EP makes sense for a 10" f/5 is at the lowest power end, i.e. super/ultra-wide at 27-34mm.