A trip round some winter nebulae

[Owmuchonomy]

11 hours ago, GavStar said:

I’m not a photographer so this is a learning experience for me. It certainly seems that in NV world generally you need to think in photography terms rather than the normal visual astro approach.

I’m getting a photo visual telecompressor (aka reducer) for my refractors today with the aim to increase the speed of my system still further. 

For my 160 refractor the speed will be reduced from f3.5 to around f2.5, which I think means that around twice the light will get to the sensor and result in evern brighter images of the dim objects. 

Unlike photography, when observing in NV you can’t change the exposure time (clearly) so you need to speed the system up to get more light in.

However, the downside of increasing the speed is that the magnification of my system (using my 55mm plossl) will reduce from 20x to 15x (and fov will increase) which will make smaller features such as the horsehead and the cone more difficult to see. For big objects, smaller scopes are good because you can get fast speed and big fov. You can’t change the fov and keep the speed without changing the scope since the NV monoculars are a fixed 40 degree fov eyepiece.

But for smaller objects, eg galaxies, planetary nebula, ideally you do want image scale as Stu says. In that case you still generally want fast speed so the answer is to buy a bigger scope - aperture fever again.

In practice, what seems to happen is that NV users in the US have 2-3 scopes to use with NV (for very big, big and smaller objects) and just the one eyepiece, which is for US users the monocular itself, for me it’s a 55mm plossl attached to my NV monocular. (US tend to use the monocular direct into the diagonal which gives a 27mm eyepiece)

I use this different approach because in Europe we are restricted to what NV monoculars we can buy. US users prefer direct because they say having an eyepiece and the NV together in the diagonal is unwieldy- however I find it fine, the NV eyepiece is really light and not that big compared to some of the heavyweight eyepieces. 

NV is a bit strange - you want a change in magnification and image scale - don’t change the eyepiece, change the scope!

Well you learn something new every day. I never knew you could adapt NV gear for use with our scopes.  Who supplies the gear in the UK and where can I learn more. It is quite intriguing. What a great thread. The Monkey Head is inverted in Gavin's picture by the way.

[PeterW]

Have a read of Gavin’s posts from the past few months. The Cloudynights Electronically Assisted forum is also a good source of info. Gavin knows where you can get new stuff, I got mine from a second hand section in hunting forum.... though you get what’s available and have no idea about the specs you’ll get.

For hydrogen nebulae there is no better solution.

good luck

Peter

[GavStar]

40 minutes ago, Owmuchonomy said:

Well you learn something new every day. I never knew you could adapt NV gear for use with our scopes.  Who supplies the gear in the UK and where can I learn more. It is quite intriguing. What a great thread. The Monkey Head is inverted in Gavin's picture by the way.

Here’s my first thread on NV which gives details of my setup. I struggled to get anything new in the UK so got my from Luxembourg - it arrived within a day or so. 

The tnvc televue adapter to attach it to my eyepieces - that took quite a bit longer...

 

[Stu]

2 hours ago, Owmuchonomy said:

The Monkey Head is inverted in Gavin's picture by the way.

Yes, from various searches I've done I think I can see that now. I sort of see a monkey head the proper way up, but find the one I see in Gavin's version a lot funnier  

[Owmuchonomy]

13 hours ago, Stu said:

Yes, from various searches I've done I think I can see that now. I sort of see a monkey head the proper way up, but find the one I see in Gavin's version a lot funnier  

I like your view better Stu!