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4" refractor vs. 4" Mak

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#26 BillP

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Posted 04 March 2018 - 03:19 PM

 

snip...

 

Re: focal ratio, FOV etc. A 4" Synta Mak has a focal length of 1300mm. A Synta Dob is typically 1200mm. So to call the FOV of the Mak "tiny" in comparison to a Dob seems like an exaggeration to me. It helps that the Dob can take 2" EP's but Maks have an ace up their sleeve too: you can put a focal reducer on it. This will help with both FOV and photographic speed.

 

My choice would be the Mak.

Can you post a link to an example?   I have a 5" ETX 125. Might like to try that.   Only heard of Focal reducers for SCTs.

 

 

Picture of adapters:

https://www.cloudyni...ucer/?p=1941190

 

Picture of TFOV results:

https://www.cloudyni...back/?p=2040870


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#27 Crow Haven

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Posted 04 March 2018 - 03:52 PM

The little C90 is also capable of wider views as was discussed at length on the "Something for Nothing" thread a few years back.  grin.gif

https://www.cloudyni...ron-c90/page-44

I enjoyed the views!  I happened to have most of the parts on hand...so why not try it. The 4" Mak could be a great travel scope and with a FR attached even more versatile.

Attached Thumbnails

  • c90_wideviewsetup.jpg
  • c90_sctvisualbk.jpg


#28 jgraham

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Posted 04 March 2018 - 04:31 PM

" I forgot to add that ill be using it for EAA as well."

 

Hmmm, that adds a little different twist. Maks are a bit slow for EAA. A refractor would be a better match, but it would need to be either an Apo or an ED and I'd add a focal reducer. My grab'n go EAA system is a little Orion 4.5" f/4 StarBlast on an LXD75 mount fitted with a Revolution Imager 2....

 

LXD75 StarBlast RI2 (9-25-2016)-2.jpg

 

...simple, lightweight, and easily reaches deeper than my 16" Dob.

 


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#29 nickcodybarrett

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Posted 04 March 2018 - 06:55 PM

 

 

 

For Planetary, Lunar, and DSO I'd go with  short Focal Length ED Refrator as the shorter F/L and ability to use longer 2" Eyepieces (to their fullest) is something the Mak isn't able to do.

The 4" ED will also cool faster although not a huge difference.

Oh I forgot to mention Achro. I cant afford an ed right now.

 

5" short tube newt.

 

Bingo.

 

A 130 mm F/5 with a decent mirror and a 2 inch focuser. No CA, much faster than the Mak or the refractor for EAA and very rugged.

 

I've owned several.. It's scary sometimes how good they can be. I remember one night under dark skies.. I was doing the low power, wide field thing with my NP-101 and swapped it out for a 130 mm, F/5 Newtonian with the 31 mm  Nagler and a paracorr. I wasn't giving up much with the $200 scope.

 

The closest thing there is to a poor man's 4 inch apo.

 

 

 

Jon

 

You said that at just the right time. I was planning on selling my Avx 8" Newt but today I doubled the length on the tripod legs(something I've never done before) and it was an entirely new telescope. Turns out everything was just awkward. Now I'm completely comfortable. I'll probably just use it for EAA instead.

 

avx.JPG


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#30 jgraham

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Posted 04 March 2018 - 08:02 PM

That'll work.


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#31 RalphMeisterTigerMan

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Posted 05 March 2018 - 04:30 AM

It would be nice if an "all purpose" do it all telescope existed. But they do not. Unless you have a budget for Astronomy like a billionaire, than selecting the right telescope for "you" is all about compromise and making the right choices.

Do you sacrifice rich-field, wide-field viewing for long focal length high magnification lunar and planetary views. Grab and go means as small, light-weight and portable as possible...but it would be nice to still have some decent aperture.

A short focal length Achro with a 2" focuser will allow you wide-field deep-sky viewing without the need for a bulky German equatorial mount or a pricey computerized altaz mounting. 

Also, will you be viewing from light-polluted skies, or are you fortunate enough to have reasonably dark skies. Many of us have, or had to, drive a considerable distance to a dark sky observing site.

Are you married and have kids that would like to come along to do some viewing?

 

Some telescope shops have a 2-week return policy, as long as there is no damage. And yes, I do know such a place and am a friend of the owner. This gives you chance to try the scope out. If it doesn't fit your viewing "lifestyle", you can return it for something more suitable for you.

 

Good-luck and I hope it all works out for you.

 

RalphMeisterTigerMan



#32 Jon Isaacs

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Posted 05 March 2018 - 05:12 AM

You said that at just the right time. I was planning on selling my Avx 8" Newt but today I doubled the length on the tripod legs(something I've never done before) and it was an entirely new telescope. Turns out everything was just awkward. Now I'm completely comfortable. I'll probably just use it for EAA instead.

 

 

With my 8 inch F/5, I kept the legs short but rather than standing, I sat comfortably in an adjustable observing chair..  If you don't have one, it might be worth considering.  I use mine with every telescope I own, every night.

 

Jon

5867928-jon with the Konus.jpg

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#33 izar187

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Posted 05 March 2018 - 10:21 AM

My 8" f5 is set up in alt-az for standing, leaning and/or sitting... and looking straight into the focuser at zenith.

The range of ep positions on this scope is small enough, that with the focuser rotated right, all works.   



#34 aeajr

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Posted 05 March 2018 - 11:06 AM

 

 

snip...

 

Re: focal ratio, FOV etc. A 4" Synta Mak has a focal length of 1300mm. A Synta Dob is typically 1200mm. So to call the FOV of the Mak "tiny" in comparison to a Dob seems like an exaggeration to me. It helps that the Dob can take 2" EP's but Maks have an ace up their sleeve too: you can put a focal reducer on it. This will help with both FOV and photographic speed.

 

My choice would be the Mak.

Can you post a link to an example?   I have a 5" ETX 125. Might like to try that.   Only heard of Focal reducers for SCTs.

 

 

Picture of adapters:

https://www.cloudyni...ucer/?p=1941190

 

Picture of TFOV results:

https://www.cloudyni...back/?p=2040870

 

Oh well:  From the link:

 

Does not fit Meade ETX's or some Celestron Maks, but does fit the
Celestron C90 Mak and Nexstar 127 SLT Mak. Check the diameter of
your scope's male threads, #SMSA fits 44.5mm threads.

 

 

 

Doesn't matter.   I have other scopes for that wide view need.   



#35 BillP

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Posted 05 March 2018 - 11:44 AM

It would be nice if an "all purpose" do it all telescope existed. But they do not. Unless you have a budget for Astronomy like a billionaire, than selecting the right telescope for "you" is all about compromise and making the right choices. ...

 

Very True waytogo.gif  IMO though, if wanting a scope with some aperture, an 8" f/5 Newt is a good all arounder.  Needs a Paracorr or other coma corrector since f/5.  But this scope is relatively small, super small if you build a Dob platform for it, handles magnifications up to 205x and more with no effort, collimation is not overly sensitive since not faster than f/5, and can achieve almost a 2.4 degree TFOV with a 31T5 or similar (6.2mm exit pupil).  If you don't need the aperture, then a simple 102mm f/9.8 achromat is really quite nice on just about everything and gets you a 2.7 degree TFOV with a 40mm 70 degree wide field with a nice 4mm exit pupil.

 

If you want a compromise point between these two then the Explore Scientific David H. Levy 152mm Comet Hunter f/4.8 Mak-Newt is a steal for about $700 (OTA) from Woodland Hills and you get a nice flat and correct FOV and you can get a 3.3 degree TFOV with a 31T5.  Otherwise there are plenty of 6" f/5 and f/6 Newts out there for around $300 (OTA) -- I would go with the f/6 as can get by without a Paracorr at that focal ratio and will get a 2.9 degree TFOV with a 40mm 70 degree AFOV wide field (6.7mm exit pupil).


Edited by BillP, 05 March 2018 - 11:45 AM.

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#36 tomykay12

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Posted 05 March 2018 - 11:47 AM

Sounds to me that you need a couple different scopes. Car shopping analogy; I'd like a car that can carry 15 friends or a load of gravel, is a convertable, does off road rock climbing and fording well, can take a girl to the prom, is fun on the twisties, and gets 50 mpg. Oh yea, I'd like to race it once in a while on the weekends.

On a more positive note, since you are a reflector guy, Jon's suggestion of a 5 or 6" f/5 newt on an alt az mount makes alot of sense.


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#37 treadmarks

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Posted 05 March 2018 - 01:18 PM

Oh well:  From the link:
 
Does not fit Meade ETX's or some Celestron Maks, but does fit the
Celestron C90 Mak and Nexstar 127 SLT Mak. Check the diameter of
your scope's male threads, #SMSA fits 44.5mm threads.

 
 
 
Doesn't matter.   I have other scopes for that wide view need.

There is one for ETX scopes: ETX adapter



#38 aeajr

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Posted 05 March 2018 - 01:36 PM

Thanks



#39 Richard Whalen

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Posted 05 March 2018 - 01:49 PM

I would look for a good used 100mm or so ed scope around f7 for EAA. Also makes a decent grab and go scope.


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#40 nickcodybarrett

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Posted 05 March 2018 - 06:35 PM

It would be nice if an "all purpose" do it all telescope existed. But they do not. Unless you have a budget for Astronomy like a billionaire, than selecting the right telescope for "you" is all about compromise and making the right choices.

Do you sacrifice rich-field, wide-field viewing for long focal length high magnification lunar and planetary views. Grab and go means as small, light-weight and portable as possible...but it would be nice to still have some decent aperture.

A short focal length Achro with a 2" focuser will allow you wide-field deep-sky viewing without the need for a bulky German equatorial mount or a pricey computerized altaz mounting. 

Also, will you be viewing from light-polluted skies, or are you fortunate enough to have reasonably dark skies. Many of us have, or had to, drive a considerable distance to a dark sky observing site.

Are you married and have kids that would like to come along to do some viewing?

 

Some telescope shops have a 2-week return policy, as long as there is no damage. And yes, I do know such a place and am a friend of the owner. This gives you chance to try the scope out. If it doesn't fit your viewing "lifestyle", you can return it for something more suitable for you.

 

Good-luck and I hope it all works out for you.

 

RalphMeisterTigerMan

There is an all purpose telescope. It's called a 20" obsession on an eq table.

 

I live in perfectly dark skies, they serve me well.

 

And no I'm 16, I sure hope I don't have a wife and kidslol.gif


Edited by nickcodybarrett, 05 March 2018 - 06:36 PM.

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#41 nickcodybarrett

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Posted 05 March 2018 - 06:37 PM

 

You said that at just the right time. I was planning on selling my Avx 8" Newt but today I doubled the length on the tripod legs(something I've never done before) and it was an entirely new telescope. Turns out everything was just awkward. Now I'm completely comfortable. I'll probably just use it for EAA instead.

 

 

With my 8 inch F/5, I kept the legs short but rather than standing, I sat comfortably in an adjustable observing chair..  If you don't have one, it might be worth considering.  I use mine with every telescope I own, every night.

 

Jon

 

Well I checked and about the lowest the scope will go is just under my standing height. I wouldn't be able to use a chair. Note the stepping stool.



#42 mandopickr

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Posted 05 March 2018 - 10:11 PM

I have a 4" achro (f/6.5) and a 4" mak. I view dso's, and both these are used for their portability. I have right angle finder scopes on both.

The achro gets used the most of these two. It is just more suitable for dso's, not a knock against the mak. I can use the refractor ota for pointing, the field of view is wider, it accepts 2" eps, and there is a slight light grab advantage. I use a lighter azimuth mount for the achro, a twilight I for the mak. With that setup, the achro is significantly lighter (but the mak and tw I are certainly not heavy by any means).

 

If I were a viewer of planets, I might feel totally different.  And I won't be selling either anytime soon.

 

FWIW



#43 jgroub

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Posted 06 March 2018 - 12:38 PM

Telescopes are tools so you pick the tool for the task.

 

Wide field vs. high mag

 

CA vs. Coma

 

Physical size and weight.

 

Clear aperture vs. Obstructed aperture.  

 

I would be looking at a 4.5" Mak vs. a 4" refractor from an aperture point of view.

 

 

If the main use is for EAA you should really be posting this in the EAA forum where the unique requirements of this approach can be best addressed.

https://www.cloudyni...-and-equipment/

Good analysis, Ed.  However, FYI, I've done the math and my 5" Mak gathers about the same light as a 4" refractor, so it's 5 to 4, not 4.5 to 4.  


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#44 jaraxx

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Posted 06 March 2018 - 03:09 PM

Unite the worlds. 

Be patient and hunt around the used sites, ebay, Craig's list, Salvation Army, etc. Find you a decent 127mm Mak (or thereabouts) and a ST 80 (or thereabouts). The goal is two scopes used for the price of a single new. Use the ST 80 as a finder for the Mak. The Mak will let you move up close and personal while the ST 80 will give context. The two together will weigh about 12 lbs.

And you can always use them separately.


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#45 jgroub

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Posted 06 March 2018 - 03:17 PM

Unite the worlds. 

Be patient and hunt around the used sites, ebay, Craig's list, Salvation Army, etc. Find you a decent 127mm Mak (or thereabouts) and a ST 80 (or thereabouts). The goal is two scopes used for the price of a single new. Use the ST 80 as a finder for the Mak. The Mak will let you move up close and personal while the ST 80 will give context. The two together will weigh about 12 lbs.

And you can always use them separately.

Which is exactly what I've done with mine.  To me, the combo of the two is deadly, and the two make the perfect small grab-and-go scope.  

 

20150122_172806.jpg

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#46 jaraxx

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Posted 06 March 2018 - 05:34 PM

 

Unite the worlds. 

Be patient and hunt around the used sites, ebay, Craig's list, Salvation Army, etc. Find you a decent 127mm Mak (or thereabouts) and a ST 80 (or thereabouts). The goal is two scopes used for the price of a single new. Use the ST 80 as a finder for the Mak. The Mak will let you move up close and personal while the ST 80 will give context. The two together will weigh about 12 lbs.

And you can always use them separately.

Which is exactly what I've done with mine.  To me, the combo of the two is deadly, and the two make the perfect small grab-and-go scope.  

 

 

Jon - very cool!

Nick - As you"re a reflector guy, this way you get experience with the Mak and the refractor worlds!


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#47 GeneT

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Posted 06 March 2018 - 07:25 PM

It really depends on budget because a premium 4” frac will be at least 2x the price of a Mak. Every scope is a trade off in one way or another.

Given your two desired choices, I would go with a good quality refractor. 



#48 Tony Flanders

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Posted 06 March 2018 - 07:49 PM

There is an all purpose telescope. It's called a 20" obsession on an eq table.

Hardly! For one thing, that's not going to be a good astrophotography rig without major modifications. Standard Dobs aren't rigid enough for astrophotography, and generally don't have a very wide fully illuminated field.

More to the point, a 20-inch Dob is too big to observe many objects. Consider the Pleiades just as one example.
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#49 nickcodybarrett

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Posted 06 March 2018 - 08:18 PM

 

There is an all purpose telescope. It's called a 20" obsession on an eq table.

Hardly! For one thing, that's not going to be a good astrophotography rig without major modifications. Standard Dobs aren't rigid enough for astrophotography, and generally don't have a very wide fully illuminated field.

More to the point, a 20-inch Dob is too big to observe many objects. Consider the Pleiades just as one example.

 

Well they may not be the best astrographs but the pictures on  obsessions website are still pretty good for me.



#50 Knasal

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Posted 06 March 2018 - 08:46 PM

Pictures on any website trying to sell you something *always* look good.

 

Kevin




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