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Baader MK 1V zoom 8-24


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Thanks for reading, I am trying to establish the fov at 24mm for this ep?  Baader say 48deg but I have seen independent testers clain it is as narrow as 40deg! (other testers seem to confirm 48degs!)  Can anyone confirm which is correct please? that's quite a difference!  I think 48 deg at 24mm  to 68 deg at 8mm sounds excellent.  40 deg might be a bit rubbish so it's a deal breaker.  (I have ordered a cheap £20 8-24mm from Ebay that's 40-60 deg to give me an idea of what to expect, which will help me to decide).  I don't do a lot of stargazing due to weather and time constraints and I tend to spend more time trying various different ep's and popping in the binoviwere just to compare etc, than I do actually observing!  This zoom could maybe replace all my other ep's apart from one widefield to use finding objects.  I had a tv 8-24mm a long time ago on an 8 inch F5 dob and I remember that was great fun especially on the moon, but now I've got a 127mm mak so fov will be tighter due to higher mag.

Thanks everyone!

 

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Problem with measuring of apparent field of view of eyepiece is in the way it is measured.

It also depends on what we mean when we say apparent field of view.

For example you could measure apparent field of view by using true field of view (probably easiest and most common method) - like drift method. It measures time it takes for star to drift across the true field of view - thus giving one true angle on the sky that view covers. Then it is simple matter of multiplying with magnification.

There are couple of issues with this approach:

1. Are you certain you know exact focal length of telescope as you need it for magnification calculation?

2. Are you certain that manufacturer of eyepiece did not round up/down their EP focal length - is it really 24mm or maybe 23.8mm or perhaps 24.1?

3. Is there geometric distortion in image that eyepiece renders?

All of these can change AFOV result.

Then there is an issue of what you mean by field of view? That can also be defined in two different ways and actually have different values for same eyepiece.

First way to define it would be: take eyepiece without telescope and just look at it against white wall. You will see a white circle surrounded by field stop. Take white circle and put it on the wall and look at it without eyepiece. Once these two circles appear same in size to you - you can calculate what angle circle subtends.

Other is actual TFOV that you see in night sky - again subject to magnification.

These two can be different due to point 3 above - but which one is more important to you? One has to do with "immersion" - how big image is compared to framing (field stop). Other is to do with how wide true field of view you can achieve.

All of the above is just to explain why there are different measurements of AFOV of eyepiece and what they mean - depending on method used.

For your particular problem - if you think that 40ish degrees at 24mm will be too narrow - I suggest you start looking at this eyepiece as being 8mm - 20mm zoom instead of 8mm-24mm.

Get yourself 24mm or longer FL eyepiece to serve you as wide field / finder EP and use Baader zoom for everything else.

 

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9 minutes ago, vlaiv said:

Problem with measuring of apparent field of view of eyepiece is in the way it is measured.

It also depends on what we mean when we say apparent field of view.

For example you could measure apparent field of view by using true field of view (probably easiest and most common method) - like drift method. It measures time it takes for star to drift across the true field of view - thus giving one true angle on the sky that view covers. Then it is simple matter of multiplying with magnification.

There are couple of issues with this approach:

1. Are you certain you know exact focal length of telescope as you need it for magnification calculation?

2. Are you certain that manufacturer of eyepiece did not round up/down their EP focal length - is it really 24mm or maybe 23.8mm or perhaps 24.1?

3. Is there geometric distortion in image that eyepiece renders?

All of these can change AFOV result.

Then there is an issue of what you mean by field of view? That can also be defined in two different ways and actually have different values for same eyepiece.

First way to define it would be: take eyepiece without telescope and just look at it against white wall. You will see a white circle surrounded by field stop. Take white circle and put it on the wall and look at it without eyepiece. Once these two circles appear same in size to you - you can calculate what angle circle subtends.

Other is actual TFOV that you see in night sky - again subject to magnification.

These two can be different due to point 3 above - but which one is more important to you? One has to do with "immersion" - how big image is compared to framing (field stop). Other is to do with how wide true field of view you can achieve.

All of the above is just to explain why there are different measurements of AFOV of eyepiece and what they mean - depending on method used.

For your particular problem - if you think that 40ish degrees at 24mm will be too narrow - I suggest you start looking at this eyepiece as being 8mm - 20mm zoom instead of 8mm-24mm.

Get yourself 24mm or longer FL eyepiece to serve you as wide field / finder EP and use Baader zoom for everything else.

 

Yes thanks.  I have a 24mm hyperion and that gives excellent views In the F12 Mak as a finder and thinking of the zoom as an 8-20 that's still a nice ep.  Also, my tfov may be a little larger because I have replaced the diagonal with a Tak prism which I believe shortens the light path so therefore the focal length of the scope a bit (enough to notice?).  Thanks for that....

Dave

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10 minutes ago, davekelley said:

Yes thanks.  I have a 24mm hyperion and that gives excellent views In the F12 Mak as a finder and thinking of the zoom as an 8-20 that's still a nice ep.  Also, my tfov may be a little larger because I have replaced the diagonal with a Tak prism which I believe shortens the light path so therefore the focal length of the scope a bit (enough to notice?).  Thanks for that....

Dave

With Mak you might get slightly shorter FL or longer FL, I'm not sure. That is because FL depends on distance between mirrors and using diagonal with less optical path means you need to take mirrors further apart to find focus (again, I'm not 100% sure on that). On other telescope designs, using diagonal with shorter light path won't have any impact on FL of objective what so ever.

In either case - I doubt you'll see any change in magnification.

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Thanks.  I'll have a play with the cheap nasty £20 zoom and see how I get on with 40 degs at 24mm and 60deg at 8mm and I suspect I may be happy with the Baader plus my 24mm Hyperion.  I want to simplify.  I also intend to seel my other eyepieces and save and buy some Canon 15x50 is bins.  That'd be my total kit, stripped down to basics, 127 mak, 24mm Hyperion, Baader Zoom, Telrad, 9x50 90 deg finder, hand controller, Canon 15x50 bins!  (I have the azgtiwifi but I prefer using the hand controller rather than messing about with mu phone and the goto is rubbish anyway but tracking is nice to have).

Just need some clear, dark(ish) skies now!  (we get about 4hrs at this time of year!)

Cheers

Dave

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I bought a Baader Hyperion Zoom (mk IV) so that we didn't have to keep swapping eyepieces/filter. Works fine, but being very short-sighted I can't see the full field of view with my specs on. Not a major issue, as it's easy enough to remove my specs & refocus - a small tweak in focus is needed anyway when going from 24x to 8x.

Just a thought...

Cheers
Ivor

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13 minutes ago, Aramcheck said:

I bought a Baader Hyperion Zoom (mk IV) so that we didn't have to keep swapping eyepieces/filter. Works fine, but being very short-sighted I can't see the full field of view with my specs on. Not a major issue, as it's easy enough to remove my specs & refocus - a small tweak in focus is needed anyway when going from 24x to 8x.

Just a thought...

Cheers
Ivor

Yes I find I always remove my specs. and tweek focus a bit with any eyepiece or binoculars I can't  get along with viewinf wjile wearing my specs.  Of course it won't be such an issue when I'm not constantly swapping eyepieces I suppose.

 

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When I last owned a Baader 8-24 zoom (I think I've owned 3 over the years !) I generally liked it and was expecting the narrower AFoV at the long FL end of course. What I found slightly annoying was that the field stop edge was rather fuzzy and ill-defined at the longer focal lengths as well. It's a small thing but I do prefer a sharp field stop in my eyepieces.

I guess with a zoom the field stop is moving with the lens elements so to expect it to be razor sharp right across the range of FL's is a big ask :dontknow:

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The Baader zoom is quite expensive compared to some of the competition so I can understand why you really want to do your homework on it. I was in a fortunate position where I was able to borrow one (thanks @Ken82), and it took me about ten minutes of using it to have me scurrrying to Flo to place an order. So if you can go to a club and have a look through one this will give you a better impression.

My view is that the narrow fov at 24mm is a bit annoying so you'll want a better ep for widefield, and likewise down at the bottom end a dedicated 4 or 6 mm will show planets and split tight doubles much more effectively, but in-between these ranges the Baader is excellent and so flexible. My current EPs are 4, 7, 8-24 and 30. I reckon the Baader is in the scope for around 50% of the time.

PS: I personally don't bother much with the dedicated Barlow though.

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On 28/06/2020 at 12:39, davekelley said:

Yes thanks.  I have a 24mm hyperion and that gives excellent views In the F12 Mak as a finder and thinking of the zoom as an 8-20 that's still a nice ep.  Also, my tfov may be a little larger because I have replaced the diagonal with a Tak prism which I believe shortens the light path so therefore the focal length of the scope a bit (enough to notice?).  Thanks for that....

Dave

Ive done similar and it works for me, Hyperion zoom and a 40mm W/O Swan. was what I was aiming for. However I got a wider 28/68 to counter the narrow 24mm of the zoom.  Mines an f10

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  • 2 weeks later...
On 04/07/2020 at 21:56, DeathWarpedUp said:

Ive done similar and it works for me, Hyperion zoom and a 40mm W/O Swan. was what I was aiming for. However I got a wider 28/68 to counter the narrow 24mm of the zoom.  Mines an f10

To be fair I'm not sure my Skymax 127 can take any higher mag than 150x in normal circumstances, so I'd really be looking at the zoom as a 10-20mm!  Still,  with the 24 Hyperion and then the zoom that does cover every focal length I ever need.  I still think I'll be looking out for one, maybe a used one.

 

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