Baader Zoom or Fixed FL EP for Planets?

[PeterC65]

3 hours ago, Louis D said:

Try putting a foam grip for handlebars or foam tape over the end of the peg.  I've found it helps dampen the contact shock from your fingertip as you search for best focus.

Good suggestion. I will add some foam. Glow in the dark foam would be handy if there is such a thing!

[bosun21]

1 hour ago, PeterC65 said:

@Second Time Around and @bosun21, the Baader Zoom was my first EP purchase. It is a lovely piece of kit, and very versatile.

I also felt the need for a low magnification EP which would allow me to see the maximum TFoV that is possible with the Skymax 127 (about 1 degree) and for this I plumped for a Celestron 40mm Omni. With this EP, the TFoV is limited by the scope rather than the EP but the 40mm FL gives me a 3.4mm exit pupil and I've read that maximising the exit pupil size is useful when using filters, particularly UHC filters, which does seem to be the case. I find that I use the Celestron 40mm almost as much as the Baader Zoom so I think I was right to purchase something with a longer FL and wider TFoV than the Baader Zoom can achieve.

Right now I just have these two EPs. I think they give me good coverage but not having anything else to compare them with keeps making me wonder what I might be missing. I've order a couple of Baader Classic Orthos (6mm and 10mm) to give me an alternative at the high magnification end of the Baader Zoom and to see what orthoscopic EPs are all about.

The slippery slope continues to beckon however, and I am wondering whether there may be merit in getting a 24mm 68 degree EP which should give me the same maximal TFoV as the Celestron 40mm but with a higher magnification. Someone should probably cut up my credit card!

I went for the 32mm Celestron Omni as on the Celestron website it states that due to the 1.25” barrel size the 32mm and the 40mm will show the same area of sky

[Stu]

3 hours ago, bosun21 said:

I went for the 32mm Celestron Omni as on the Celestron website it states that due to the 1.25” barrel size the 32mm and the 40mm will show the same area of sky

That’s correct, and for shorter focal ratio scopes it’s a good choice. For filtered views on a Mak or SCT the 40mm is worth considering as it offers a larger exit pupil even though the field of view is about the same.

[Mr Spock]

A zoom might be convenient, but I went for image quality. I've ordered a set of Vixen SLVs - 6mm, 5mm and 4mm, for use in my 250mm. Those focal length give me x200, x240 and x300 which is just about perfect 

[bosun21]

1 hour ago, Stu said:

That’s correct, and for shorter focal ratio scopes it’s a good choice. For filtered views on a Mak or SCT the 40mm is worth considering as it offers a larger exit pupil even though the field of view is about the same.

What is the favored exit pupil?. I’ve heard so many opinions. The ideal i was told to aim for is 2 for DSO’s and down to as low as 0.5-1 for planets etc. Is there an upper limit over which the image will degrade? Sorry for all the questions 

[Ags]

It depends on your eyes. Small exit pupils (less than 1 mm) cause the muck floating in your eye to become visible. For me, these floaters mean there is no point going below an exit pupil on 1mm as they completely obscure all planetary detail, but other people just don't seem to have many floaters. 

For DSOs, I find the ideal exit pupil depends on the target and the light pollution. Planetary nebulae and globular clusters improve with more magnification in my experience, but open star clusters need lower magnification to get the framing right. Faint nebulae might need a large exit pupil (5 mm or more) combined with an Oiii or UHC filter to tease out their structures.

Edited November 14, 2021 by Ags

[Stu]

9 hours ago, bosun21 said:

What is the favored exit pupil?. I’ve heard so many opinions. The ideal i was told to aim for is 2 for DSO’s and down to as low as 0.5-1 for planets etc. Is there an upper limit over which the image will degrade? Sorry for all the questions 

Ags has answered this well, and whilst there are guidelines there are not really any hard and fast rules.

Upper and lower limits tend to be defined by you eyes. Eg approx 7mm as a maximum (or less if you are older) before you start ‘wasting light’ by the exit pupil being larger than your dilated pupil size when dark adapted. You can go bigger if you want a larger field of view but face washed out skies if you have LP, or seeing the shadow of the secondary in obstructed scopes.

At the lower end it tends to be limited by dimming of the image and floater visibility. I tend to think of 1mm as a good low end on large scopes as this still gets you to high mags eg x300 on a 300mm scope. On smaller apo refractors, 0.5mm or even less is useable so long as you do not see too many floaters. Even so it can work for doubles. Binoviewers help mitigate again floaters too.

In between, it’s a matter of optimising image scale, contrast, field of view etc. Somewhere around 2mm is supposed to give optimum views for DSOs but it varies hugely depending on the size and type of DSO. 2mm is likely good for small galaxies and planetary nebulae, but for larger clusters or faint nebulae the larger fields of view, and lower powers are needed. If a faint nebula such as the Rosette fills the field of view, there will be no edges to show contrast and so you likely won’t even seen the object.

Much depends on your skies, as larger exit pupils show a very washed out sky background if you have much LP, so upping the power can help reduce this. But, with narrowband filters, larger exit pupils (say 4 to 7mm) work better to keep the image brightness up, with the filter darkening the background brightness, which is where we come back to the point about using a 40mm vs a 32mm Plossl for narrowband filtered views in Maks and SCTs. The field of view won’t be bigger, but the image brightness should be a bit better due to the larger exit pupil.

[Mr Spock]

One of the reasons I went for a 250mm Dob rather than a refractor. Having diabetic maculopathy I have permanent floaters over my left (observing) eye and a blurred patch over the other. A brighter image helps with this somewhat. I couldn't use a refractor at high powers.

Even at 1mm it's very noticeable 

[Stu]

1 hour ago, Mr Spock said:

One of the reasons I went for a 250mm Dob rather than a refractor. Having diabetic maculopathy I have permanent floaters over my left (observing) eye and a blurred patch over the other. A brighter image helps with this somewhat. I couldn't use a refractor at high powers.

Even at 1mm it's very noticeable 

Aperture certainly helps in the battle against floaters!

[Ags]

The same reason why I have a C6 - it is the largest aperture small scope, meaning I have floater free views at around 125 magnification.

Another point related to exit pupil and planets, is that larger exit pupils mean a brighter image which means stronger color. 

Edited November 14, 2021 by Ags

[Stu]

9 minutes ago, Ags said:

The same reason why I have a C6 - it is the largest aperture small scope, meaning I have floater free views at around 125 magnification.

Another point related to exit pupil and planets, is that larger exit pupils mean a brighter image which means stronger color. 

Yep, all very true.

I love the planetary views through my FC100DC but certainly the colour on Jupiter say is stronger in my 8” f8.

[PeterC65]

For maximum sky coverage (TFoV) I went for the 40mm Celestron Omni because of the larger exit pupil size compared with shorter FL EPs. It gives me a 3.4mm exit pupil on my Skymax 127, so still not that large. Observing M42 recently (and for the first time) with an Astronomik UHC filter, the view though the 40mm Celestron Omni showed noticeably better contrast than that through my Baader Zoom at 24mm so going for the larger exit pupil size seems to be justified.

With the Skymax 127 being F11.8, the best TFoV I can get (with 1.25" EPs) is just under 1.1°. Initially I did consider upgrading to a 2" diagonal and EPs but I've since decided to accept the limitations of the scope when it comes to TFoV and stick with 1.25".

I only have two EPs at the moment, the 40mm Celestron Omni and the Baader Zoom, so don't have much to compare. This post started with a discussion about shorter FL EPs compared to the Zoom, and I now have two Baader Classic Orthos (6mm and 10mm) on order to provide a comparison at the high magnification end.

I've also been wondering about the low magnification end ...

My understanding is that a 68° EP FoV is optimal for the human eye. Any wider and you can only see part of the presented image and so have to look around within the wider image presented by the EP. Any narrower and the presented image is smaller than what your eye can take in so you see a circular image surrounded by black. I can't say I've really experienced either of these things but then I'm new to all this.

If a 68° EP FoV is optimal, and given I'm sticking with 1.25", then the TFoV will max out at a FL of 24mm. So I'm wondering whether a 24mm 68° EP might be a useful addition?

While the Baader Zoom does 24mm, the EP FoV is then 42° so the TFoV is not maximal. I'm thinking that a 24mm 68° EP will give me the maximum magnification possible whilst showing me the maximum amount of sky and using the maximum amount of retina. So the same amount of sky as the 40mm Celestron Omni but more magnified and therefore bigger by virtue of using more retina.

The downside seems to be the smaller exit pupil size with a 24mm 68° EP. It would be 2.03mm I believe rather than the 3.4mm I get with the 40mm Celestron Omni and so the image may be darker, particularly when it's been filtered.

As ever, I will only know when I can compare the two side by side!

 

[Mr Spock]

Hmm, I wonder if that's why I find my LVWs so comfortable. Apart from the easy eye relief and lack of eye position dependant aberrations, they are 65°,

[Highburymark]

On 08/11/2021 at 16:09, SuburbanMak said:

 

Thinking about the Starbase range or ponying up for a Tak Abbe and seeing if it lives up to the price...  

I’d advise waiting on the Tak Abbes. I’ve sent back my recently-bought 12.5mm, 9mm and 6mm because of dust/gunk in the glass, and am waiting to hear back. Although the views appeared to be good, there are clear and considerable imperfections when the eyepieces are examined under bright light - way more than could normally be expected. The problem has been well documented on Cloudy Nights, so it’s not just a local issue.

[Stu]

17 minutes ago, PeterC65 said:

For maximum sky coverage (TFoV) I went for the 40mm Celestron Omni because of the larger exit pupil size compared with shorter FL EPs. It gives me a 3.4mm exit pupil on my Skymax 127, so still not that large. Observing M42 recently (and for the first time) with an Astronomik UHC filter, the view though the 40mm Celestron Omni showed noticeably better contrast than that through my Baader Zoom at 24mm so going for the larger exit pupil size seems to be justified.

With the Skymax 127 being F11.8, the best TFoV I can get (with 1.25" EPs) is just under 1.1°. Initially I did consider upgrading to a 2" diagonal and EPs but I've since decided to accept the limitations of the scope when it comes to TFoV and stick with 1.25".

I only have two EPs at the moment, the 40mm Celestron Omni and the Baader Zoom, so don't have much to compare. This post started with a discussion about shorter FL EPs compared to the Zoom, and I now have two Baader Classic Orthos (6mm and 10mm) on order to provide a comparison at the high magnification end.

I've also been wondering about the low magnification end ...

My understanding is that a 68° EP FoV is optimal for the human eye. Any wider and you can only see part of the presented image and so have to look around within the wider image presented by the EP. Any narrower and the presented image is smaller than what your eye can take in so you see a circular image surrounded by black. I can't say I've really experienced either of these things but then I'm new to all this.

If a 68° EP FoV is optimal, and given I'm sticking with 1.25", then the TFoV will max out at a FL of 24mm. So I'm wondering whether a 24mm 68° EP might be a useful addition?

While the Baader Zoom does 24mm, the EP FoV is then 42° so the TFoV is not maximal. I'm thinking that a 24mm 68° EP will give me the maximum magnification possible whilst showing me the maximum amount of sky and using the maximum amount of retina. So the same amount of sky as the 40mm Celestron Omni but more magnified and therefore bigger by virtue of using more retina.

The downside seems to be the smaller exit pupil size with a 24mm 68° EP. It would be 2.03mm I believe rather than the 3.4mm I get with the 40mm Celestron Omni and so the image may be darker, particularly when it's been filtered.

As ever, I will only know when I can compare the two side by side!

 

You’ve certainly grasped all the theory behind it which is a major step. A 24mm 68 degree eyepiece would be a nice addition I think, particularly for non filtered views of clusters etc. the sky background would be a little darker than the 40 and the wider afov does feel a little less hemmed in. I have a 24mm Panoptic, but there are good other options out there, from ES especially.

[PeterC65]

31 minutes ago, Stu said:

A 24mm 68 degree eyepiece would be a nice addition I think, particularly for non filtered views of clusters etc. the sky background would be a little darker than the 40 and the wider afov does feel a little less hemmed in. I have a 24mm Panoptic, but there are good other options out there, from ES especially.

I was thinking about a Baader Hyperion 24mm or an ES 68° 24mm. The Baader has a slightly bigger field stop (28.5mm) than the ES (27.2mm) so the TFoV is a little wider, but not much. But I'm wondering whether the Baader Hyperion 24mm might be very similar (in construction) to the Hyperion Zoom that I already have and so maybe the ES would provide a more different comparator? Does anyone have a view about the Baader Hyperion 24mm versus the ES 68° 24mm?

[Ricochet]

5 minutes ago, PeterC65 said:

I was thinking about a Baader Hyperion 24mm or an ES 68° 24mm. The Baader has a slightly bigger field stop (28.5mm) than the ES (27.2mm) so the TFoV is a little wider, but not much. But I'm wondering whether the Baader Hyperion 24mm might be very similar (in construction) to the Hyperion Zoom that I already have and so maybe the ES would provide a more different comparator? Does anyone have a view about the Baader Hyperion 24mm versus the ES 68° 24mm?

In your Skymax either will probably be ok, but if you ever buy a faster telescope the ES68 will be significantly better, so long as you don't need to wear glasses when observing. As far as I am concerned the options you should be looking at are the ES68, the TV Panoptic and the APM UFF.

[SuburbanMak]

2 hours ago, PeterC65 said:

I was thinking about a Baader Hyperion 24mm or an ES 68° 24mm. The Baader has a slightly bigger field stop (28.5mm) than the ES (27.2mm) so the TFoV is a little wider, but not much. But I'm wondering whether the Baader Hyperion 24mm might be very similar (in construction) to the Hyperion Zoom that I already have and so maybe the ES would provide a more different comparator? Does anyone have a view about the Baader Hyperion 24mm versus the ES 68° 24mm?

I have the Baader Hyperion 24mm fixed, is a lovely EP in the Mak 127 and gives the max available field. It’s my main galaxy hunter. FoV is much wider than the MkIV zoom stopped to 24mm. To my eye contrast & sharpness a bit better too. 

[John]

2 hours ago, PeterC65 said:

I was thinking about a Baader Hyperion 24mm or an ES 68° 24mm. The Baader has a slightly bigger field stop (28.5mm) than the ES (27.2mm) so the TFoV is a little wider, but not much. But I'm wondering whether the Baader Hyperion 24mm might be very similar (in construction) to the Hyperion Zoom that I already have and so maybe the ES would provide a more different comparator? Does anyone have a view about the Baader Hyperion 24mm versus the ES 68° 24mm?

I've used both the Hyperion 24mm and the ES 24mm / 68 and found the ES to be noticably sharper in the outer half of the field of view in scopes faster than around F/7-ish.

I moved from the ES 24mm / 68 to the Tele Vue Panoptic 24mm (at some cost !) but really there is precious little to choose between them in performance I found. My scopes vary from F/5.3 to F/9.2.  The 24mm Panoptic is a more compact eyepiece though.

If you are not going to use the eyepiece in scopes faster than F/7 then the Hyperion will probably do fine.

 

 

 

Edited November 14, 2021 by John

[Don Pensack]

7 hours ago, PeterC65 said:

For maximum sky coverage (TFoV) I went for the 40mm Celestron Omni because of the larger exit pupil size compared with shorter FL EPs. It gives me a 3.4mm exit pupil on my Skymax 127, so still not that large. Observing M42 recently (and for the first time) with an Astronomik UHC filter, the view though the 40mm Celestron Omni showed noticeably better contrast than that through my Baader Zoom at 24mm so going for the larger exit pupil size seems to be justified.

With the Skymax 127 being F11.8, the best TFoV I can get (with 1.25" EPs) is just under 1.1°. Initially I did consider upgrading to a 2" diagonal and EPs but I've since decided to accept the limitations of the scope when it comes to TFoV and stick with 1.25".

I only have two EPs at the moment, the 40mm Celestron Omni and the Baader Zoom, so don't have much to compare. This post started with a discussion about shorter FL EPs compared to the Zoom, and I now have two Baader Classic Orthos (6mm and 10mm) on order to provide a comparison at the high magnification end.

I've also been wondering about the low magnification end ...

My understanding is that a 68° EP FoV is optimal for the human eye. Any wider and you can only see part of the presented image and so have to look around within the wider image presented by the EP. Any narrower and the presented image is smaller than what your eye can take in so you see a circular image surrounded by black. I can't say I've really experienced either of these things but then I'm new to all this.

If a 68° EP FoV is optimal, and given I'm sticking with 1.25", then the TFoV will max out at a FL of 24mm. So I'm wondering whether a 24mm 68° EP might be a useful addition?

While the Baader Zoom does 24mm, the EP FoV is then 42° so the TFoV is not maximal. I'm thinking that a 24mm 68° EP will give me the maximum magnification possible whilst showing me the maximum amount of sky and using the maximum amount of retina. So the same amount of sky as the 40mm Celestron Omni but more magnified and therefore bigger by virtue of using more retina.

The downside seems to be the smaller exit pupil size with a 24mm 68° EP. It would be 2.03mm I believe rather than the 3.4mm I get with the 40mm Celestron Omni and so the image may be darker, particularly when it's been filtered.

As ever, I will only know when I can compare the two side by side!

 

Some notes:

1) the Sky & Telescope test of the 127mm showed the actual clear aperture is about 121mm because lateral rays from the corrector diverge enough to miss the primary (this kind of Gregory-Maksutov should have had a primary mirror about a half inch larger to field all the lateral rays from the corrector), and the measured focal length at the back with the provided 1.25" diagonal and provided visual back was 1540mm.  That makes the as-delivered scope about f/12.73

2) the focal length grows on this scope with increased back focus distance.  It grows by approximately 3.75mm for every mm of additional back length.  So adding a 2" diagonal and visual back is probably going to add at least 80mm to the back focus distance (maybe more), so  that means a focal length of about 1840mm, for f/15.2

3) Hence, a 40mm eyepiece would yield about a 2.6-2.7mm exit pupil.

The way to increase the exit pupil and field size at low power is to use as short a visual back as possible and use a 1.25" prism diagonal  AND use a 40mm 1.25" eyepiece.  You can get the focal length as short as 1500mm that way (f/12.4), and get both a lower low power and a larger exit pupil.

[Louis D]

Going to a 2" visual back and 40mm SWA eyepiece easily overcomes the increase in focal length to get to a wider field of view with a Synta 127 Mak with about 40% vignetting near the edge.

[Zermelo]

On 12/11/2021 at 18:32, bosun21 said:

I have however just found a 3D printed (glow in the dark) focus knob that just slips over the existing one, Great for the £8 post

Did you source that commercially? I recall an SGL member had offered to print some himself for one or two who were interested.

[bosun21]

4 hours ago, Zermelo said:

Did you source that commercially? I recall an SGL member had offered to print some himself for one or two who were interested.

I found them on eBay

ay 

[PeterC65]

I've gone for the Explore Scientific 68 degree 24mm. I picked up the last one they had at the Widescreen Centre (the last one anyone seemed to have). Since the recent Baader price hike, the Hyperion is now £133 which is almost as much as the better rated ES.

[Don Pensack]

On 14/11/2021 at 16:55, Louis D said:

Going to a 2" visual back and 40mm SWA eyepiece easily overcomes the increase in focal length to get to a wider field of view with a Synta 127 Mak with about 40% vignetting near the edge.

Louis,

I notice the right side of each image is in better focus than the left edge.  Is your scope's objective tilted relative to the target?