DGM Optics NPB filter - my newbie thoughts

[erick (Eric)]

I was kindly lent (thanks Janoskiss) a 1.25" DGM Optics NPB filter to try out in my 8" f6 reflector. I'd followed a few threads/reviews, looked at various filters and was interested in the good reports of this filter relative to its very economical price, compared with the standards - Skyglow, OIII, UHC, Deepsky, Ultrablock etc.

DGM Optics (Seems to be only through the Omega Astrofilters site http://www.omegafiltersebuyer.com/se...ers/Categories ) says:-

"The NPB (Narrow Pass Band) filter is an Ultra High Contrast type of filter that is very effective for small and fainter emission and planetary nebula and a variety of bright nebula, especially through larger scopes."

I had two opportunities to use the filter last weekend. One under dark sky conditions after the Moon had set and one in misty skies under quarter moonlight. I used it with a 15mm Bintel (GSO) plossl and a Vixen LV 10mm eyepiece. Targets were Carina Nebula, Lagoon Nebula and Triffid Nebula.

Now, if you are expecting an expert assessment - sorry - I don't have the experience, but on one night I did have a more experienced observer with me.

My summary - I thought it was very useful. It clearly darkened the sky relative to the nebulae. Edges of a nebula were more clearly distinguished. In the moonlit sky, Carina and Lagoon were better distinguished with the filter (didn't look for Triffid that night). Under dark sky, I could convince myself that I could make out the dark lanes in Triffid. Now, the more experienced observer agreed that there was better contrast between the nebulae and the background, but thought that some of the detail of the nebulae was being lost. Light transmission seemed good, the nebulae weren't noticeably darker with the filter in place. I did notice that the focus point changed with the filter in place.

It had an interesting effect on Eta Carina - it went deep red. For fun, I turned the scope on Antares which was also a deep red colour.

All I can say is that I'd like to get one - the 2" version so I can drop the magnification to gather the whole view. Those who have no use for their 2" DGM Optics NPB filter - you might have a sale! (See the classifieds)

[matt]

Well done, Eric. Good report.

I have the 1.25" version and enjoy it very much.

It's great, for the money

[taminga16 (Greg)]

Erick, I have been toying with the idea of a DGM NPB filter and with a little push I could probably be encouraged to share shipping costs.

PM me if you are interested.

Regards Greg.

[JethroB76 (Jeff)]

I know a few here on IIS have one these, do most have it in 1.25 or 2"?
In a 12" Dob would it get more use on something in the 26-32mm range or on something 13-19mm?

[wavelandscott (Scott)]

I have a 1.25 inch one...all of my eyepieces are 1.25 inch so it was an easy choice for me...

I think highly of them if you are in the market for this type of filter.

[iceman (Mike)]

I have a 1.25" one as well. Unfortunately it doesn't see a lot of use at the moment because I'm usually imaging instead of observing

But when I have used it, I loved it.

[Tamtarn]

Originally Posted by Isdonisgood

I know a few here on IIS have one these, do most have it in 1.25 or 2"?
In a 12" Dob would it get more use on something in the 26-32mm range or on something 13-19mm?

We have a 12" dob and we have the 2" and find we use it mostly with the Nagler 17mm T4 vision is spectacular on all nebulae !! Also use it with the 27 Pano occasionally.

Used with the Pentax 10 & 7 XW's 1.25" it's great for planetary nebulae well.

You screw the filter on to the bottom of the 1.25" adapter but you need a spacer so the bottom of the EP doesn't touch the filter.

[skies2clear]

I have the 1.25" and can't use it above my 20mm fl eyepieces. It works a treat too. This may sound dumb, but I've manually held it in place over my eye (have long eyerelief EP's) when using 30 and 40mm FL's, and it works, but just to try it out. Will look at the possibility of getting a 2" one later some time,

Clear skies
Nick

[wavelandscott (Scott)]

Originally Posted by skies2clear

This may sound dumb, but I've manually held it in place over my eye (have long eyerelief EP's) when using 30 and 40mm FL's, and it works, but just to try it out.

It does not sound silly at all...I do this sometimes to to help try and "wink/blink" things out...sometimes the in/out blinking method is really helpful in finding otherwise hard to see things...

[skies2clear]

Originally Posted by wavelandscott

It does not sound silly at all...I do this sometimes to to help try and "wink/blink" things out...sometimes the in/out blinking method is really helpful in finding otherwise hard to see things...

And at times I'll just hold the filter in place to compare which filter works the best on certain objects. Far more often than not, it's the DGM NPB!

CS
Nick

[janoskiss (Steve H)]

It's good to try at bit lower powers also, near 3mm exit pupil, where there is plenty of light to spare. On larger nebs I found it a good pair-up with the 19mm Panoptic in my 8" f/6 Dob. M42 from well polluted backyard looks great through that combo.

[erick (Eric)]

Yes Steve, I was eyeing off M42 this morning as I came into work during early glimmerings of sunrise. I'm going to have a go as soon as I can get an early morning clear. I'd really like to see how well this filter rejects city light pollution.