Magic Horsehead Eyepiece

[Tweedledee]

I would love to see the Horsehead Nebula in Orion. I searched on the web about this and came across an article called the Magic Horsehead Eyepiece. This is a specification for an eyepiece which is most likely to show the elusive Horsehead Nebula. After reading the article I thought that this approach to the problem might just work.

Here are the specs for this eyepiece;
A high quality ep with few elements, high light transmission and high contrast.
Small field of view to keep the dazzling mag 1.8 Alnitak well outside the view.
Just a 5mm exit pupil to give good contrast with less chance of washing out the view as may happen with a larger exit pupil.

So, what eyepiece will do the job?
One persons Magic Horsehead Eyepiece will be different from someone elses, as it is specific to the focal ratio of the telescope. Firstly we need to have an ep of the right focal length to give a 5mm exit pupil. In an F6 scope this will be a 30mm, F5 a 25mm and F4 a 20mm. So I need a 20mm for the 10" F4 Schmidt Newtonian.

First I fancied getting a 4 element Orthoscopic, which usually has a very narrow but highly suitable field of about 43 degrees, but they seem to be available either as a 25mm which is too long or 18mm which is slightly short.

I then came across a s/h Televue 20mm Plossl at just £55 on AB&S. With green writing, this has to be the best in its class, with only 4 elements giving high light transmission and good contrast. A quick look at the specs on the TV website told me it has a slightly larger 50 degree apparent field than I had hoped but still narrow. The website also asserted that the TV Plossl is a significant improvement on other manufacturers Plossls and Orthos. So I bartered the price down to £50 inc P&P and bought it.

The 20mm TV Plossl fits all the parameters for my "Magic Horsehead Eyepiece", and may also show the Flame Nebula close by. Coupled with my Hydrogen Beta filter, it might just do the trick.

The eyepiece arrived yesterday and looks like new. This 1.25" eyepiece is tiny compared to the usual grenades I put in the focuser. It is so small, I'm worried it might get lost in the dark.

It will be a few months before the sun allows the horse some shade, but when it does I'll be ready. I know I will also need a dark site, full dark adaptation, a black out cover over my head and a lot of luck.

I would be interested to know if any one else has seen the Horsehead, and what equipment was used. Any other tips on this would be appreciated.

 

[catman161]

Useful info thanks Pete. I didn't know the horse head was able to be seen in the eyepiece.

[Teslar]

Great plan. Good luck with that

[philjay]

It is elusive the Hh and also the right conditions. I 1st tried with my old c11 a few years ago. I tried one really clear but blowy night with a combo of 40mm and 25mm eyepieces plus hbeta filter. No chance. The next night seeing was worse with a slight mist but atmospherics were stable. After a long time at the ep I detected the line of nebulosity and followed it down till i found a break in it which was the hh. Then by careful observation I could just detect the outline. I then confirmed it by slotting in the mintron and yep it wasnt my imagination.

Even with an 11" scope its elusive and you may not get it 1st time, ideally a 12" plus is best but its nice to bag it in smaller

[Tweedledee]

Thanks Phil, I bet you were well pleased.

 

I am fully aware that seeing the Horsehead with my current equipment is an extreme long shot if not an impossibility.

Being optimistic and enjoying a challenge, I figure that if I can pull together the right techniques and get lucky with a really dark sky and a moment of superb clarity, then anything is possible.

Whatever happens, I am learning new observing skills that will help in other situations with other objects, whilst adding to my armoury of tackle required for teasing out such difficult views.

Until I can afford that 20" dob, I intend to push the limits with with what I have. It would certainly be nice it it did all come together.