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Baader Mark IV Zoom and 10” Dobsonian

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#1 DanielG8686

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Posted 13 July 2020 - 01:06 PM

I want to purchase the Skywatcher 10” goto dobsonian. It is f4.7.... I was wondering if I could get away with purchasing a Baader Mark IV zoom to go with it? Or will the views be soft and full of coma? Also.. I want to get a quality product to collimate the mirrors. What is a good laser collimator that isnt going to cost a fortune? What size collimator should i get? The focuser is 2” and has a 1.25” adapter. I was told to collimate with a 1.25” collimator because it will be more precise! Not sure if thats true. Thank you!!

Edited by DanielG8686, 13 July 2020 - 02:34 PM.


#2 Taosmath

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Posted 13 July 2020 - 01:33 PM

I use my Baader Zoom on my 8" F6, 12" F5 & 17.5" F4.5 and I find the views quite acceptable.

 

Worst aspect is the limited field of view at 20mm+, but I do 90% of my Dob viewing with a BZ and a 31mm Axiom.



#3 SeattleScott

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Posted 13 July 2020 - 01:43 PM

Coma is largely a function of AFOV. It will be more evident at 8mm setting than 24mm. Coma isn’t really that bad staying below 70 AFOV.

As mentioned you will still want an eyepiece with a wider view for low power. You will also want another eyepiece or two for high power. With a 10” Dob the BHZ is a low-medium, medium and medium-high power eyepiece. You still need low power and high power.

Some people use a barlow with the BHZ for high power. A little bit of a hassle but it reportedly does sharpen the view a bit as barlows tend to do.

Scott

#4 ButterFly

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Posted 13 July 2020 - 02:08 PM

The zoom with a barlow is great for planets and doubles.  It's about 100-300x with that scope with a 2x barlow.  A nice range indeed.  At the 50-150x ordinary range at f/4.7, it helps pick a nice exit pupil to pull out features in DSOs.

 

"Full of coma" is entirely up to you and what you notice.  If you notice the coma at the low end of the zoom (~68 degrees), and it bothers you, then consider the coma corrector for that wider field low power eyepiece.  Don't go looking for it, because you may find it.

 

"Soft" is something that won't be comming from the eyepiece.  It is a nice performer in whatever I have put it in.  Learn how to collimate well and your views should be as nice as you can get.



#5 DanielG8686

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Posted 13 July 2020 - 02:30 PM

The zoom with a barlow is great for planets and doubles. It's about 100-300x with that scope with a 2x barlow. A nice range indeed. At the 50-150x ordinary range at f/4.7, it helps pick a nice exit pupil to pull out features in DSOs.

"Full of coma" is entirely up to you and what you notice. If you notice the coma at the low end of the zoom (~68 degrees), and it bothers you, then consider the coma corrector for that wider field low power eyepiece. Don't go looking for it, because you may find it.

"Soft" is something that won't be comming from the eyepiece. It is a nice performer in whatever I have put it in. Learn how to collimate well and your views should be as nice as you can get.


Thanks for your help! What is “exit pupil” exactly?

#6 SeattleScott

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Posted 13 July 2020 - 03:39 PM

Exit pupil is the size of the light cone in mm coming from the eyepiece. Generally the useful range is considered about 6-7mm down to 0.5mm. The bigger the exit pupil, the brighter things look. You can calculate exit pupil by dividing the focal length of the eyepiece (variable in the case of the zoom) with the F ratio of the scope. Different levels of magnification and brightness can be helpful for teasing out faint details.

Scott

#7 junomike

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Posted 13 July 2020 - 03:42 PM

Never heard of the colllimatation difference using a 1.25" or 2".

Use what you have and not worry about it.



#8 SeattleScott

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Posted 13 July 2020 - 03:46 PM

As for your question of a quality laser collimator, the $60-80 Chinese ones work pretty well, but I ended up stepping up to a Howie Glatter TuBlug barlowed collimation laser. Around $150-200 depending on 1.25 or 2” versions. If you get the 1.25” you should also consider a self centering 1.25” adapter.

Scott

#9 DanielG8686

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Posted 13 July 2020 - 03:47 PM

Exit pupil is the size of the light cone in mm coming from the eyepiece. Generally the useful range is considered about 6-7mm down to 0.5mm. The bigger the exit pupil, the brighter things look. You can calculate exit pupil by dividing the focal length of the eyepiece (variable in the case of the zoom) with the F ratio of the scope. Different levels of magnification and brightness can be helpful for teasing out faint details.

Scott


Oh ok! What laser collimator would you recommend for my 10” Skywatcher Dobsonian. Something that is nice and easy to work with, but isnt hurting the bank too much. I read a lot of people complaining about the cheap ones having too large of beams and such. Thank you

#10 SeattleScott

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Posted 13 July 2020 - 03:48 PM

We must have been posting at the same time. See my post above.

#11 DanielG8686

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Posted 13 July 2020 - 03:52 PM

As for your question of a quality laser collimator, the $60-80 Chinese ones work pretty well, but I ended up stepping up to a Howie Glatter TuBlug barlowed collimation laser. Around $150-200 depending on 1.25 or 2” versions. If you get the 1.25” you should also consider a self centering 1.25” adapter.

Scott


My skywatcher will come with a 1.25” adapter for the focuser. Will that work fine with a 1.25” collimator?

#12 SeattleScott

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Posted 13 July 2020 - 04:11 PM

It will work ok but usually that involves a set screw pushing on the side to hold the 1.25” eyepiece in place. Well pushing on one side can push something a little off center. Hence a self centering adapter is considered better. Or pay more for the 2” version. But a self centering adapter is cheaper than upgrading to 2” and you can use it with 1.25” scopes.

Edited by SeattleScott, 13 July 2020 - 04:12 PM.



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