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is 4 inch enough for serious planet observing?

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#26 BillP

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Posted 16 November 2020 - 07:43 PM

...the 4 inch F11 is only 700 euros. they also have a 4 inch f8 ED for 1000 euros. 

Actually I get more and more excited about the 4 inch f11.2.......

You should make a 100mm mask for your current 152 f/5.9 and see how the planets look for yourself.  That mask will bring it down to an f/9.2 instrument so should tame a lot of the CA. 


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#27 N-1

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Posted 16 November 2020 - 07:44 PM

A 5mm, 6mm, and 7mm will be your planetary workhorses!  Or a 12mm, 15mm, 18mm with a TV 2.5x Powermate grin.gif

I think I have those covered. A 5mm Pentax XO, a 6mm Supermono, and a 7mm Pentax SMC ortho.

Plus various Bak4 marbles from China waiting to be put in a housing and tested...
Just a bit worried about the old GP mount with that moment arm but we shall see.



#28 t.r.

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Posted 16 November 2020 - 07:55 PM

A 5mm, 6mm, and 7mm will be your planetary workhorses! Or a 12mm, 15mm, 18mm with a TV 2.5x Powermate grin.gif

Or a Televue Nagler 3-6 Zoom!
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#29 CHASLX200

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Posted 16 November 2020 - 08:07 PM

My  FS102 Taks did a fine job on planets. But they don't come close to my much bigger Zambuto Newts in the 11" to 14.5" sizes on the planets. 350x is about the max in a good 4" before the image starts to get dim for Jupiter and Saturn, Mars when big and close can handle higher power as will Venus vs Jupiter and Saturn in a 4". While on my best nites a 14.5" Newt can do 1150x on the planets.  My 3mm to 5mm eyepieces gets used the most as i am a planet viewer 90% of the time and lucky to have some world class seeing.


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#30 Brent

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Posted 16 November 2020 - 09:09 PM

I'm with the folks who advise to hold off on the 4". I also have a Questar 3-1/2 and a pretty nice 4" (NP-101). Both are excellent samples, I believe. I also live in an area where the seeing is usually turbulent. I use the Questar far more often than the refractor. And in side-by-side comparisons, on nights of good-enough seeing, the Q pretty much holds its own against the 4" once everyone is cooled down. In the best seeing, the 4" will pull out ahead, but most of the time it only bests the Questar in brightness. Most of the time I wonder why I have both. 

 

I found myself seriously considering a 120 to replace the 4". 

 

But, on the other hand, refractors are da bomb, and if you want one and can afford it, why not?


Edited by Brent, 16 November 2020 - 09:10 PM.

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#31 eblanken

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Posted 16 November 2020 - 10:01 PM

Hi Michiel & All,

 

I very much agree with all the following quotes:

 

Whether a telescope of any given size is enough for serious observing depends more on the observer than the aperture... 

 

 

Clear skies!

Thomas, Denmark

 

 

Hmmm...what was that sound?  Oh, it was a nail being hit on the head waytogo.gif

 

 

waytogo.gif

 

One can always argue bigger is better and there's a lot of truth in that.

 

But serious observing is about the observer and not the equipment and some amazing planetary sketches are done with ~60  mm refractors. 

 

I think Thomas has made some from his island in the Baltic.

 

Jon

These guys all really know their stuff and have my respect and admiration.

 

Your Questar sets the bar pretty high, but an unobstructed 100mm ED scope with excellent figure will most likely best it at least when the sky conditions allow !!!

 

All-the-Best,

 

Ed (aka eblanken)


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#32 eblanken

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Posted 16 November 2020 - 10:03 PM

Hi Michiel & All,

 

I very much agree with the wisdom of the other camp expressed in the following quote as well (You asked a great question):

 

I'm with the folks who advise to hold off on the 4". I also have a Questar 3-1/2 and a pretty nice 4" (NP-101). Both are excellent samples, I believe. I also live in an area where the seeing is usually turbulent. I use the Questar far more often than the refractor. And in side-by-side comparisons, on nights of good-enough seeing, the Q pretty much holds its own against the 4" once everyone is cooled down. In the best seeing, the 4" will pull out ahead, but most of the time it only bests the Questar in brightness. Most of the time I wonder why I have both. 

 

I found myself seriously considering a 120 to replace the 4". 

 

But, on the other hand, refractors are da bomb, and if you want one and can afford it, why not?

Cheers,

 

Ed (aka eblanken)



#33 eblanken

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Posted 16 November 2020 - 10:09 PM

Hi Michiel & All,

 

So much good advice here in this thread. I'd do the mask experiment first. And buy the 3mm-6mm TV Zoom next if that suits you  for the 152mm. And try some filters in the 152mm as well.

 

You should make a 100mm mask for your current 152 f/5.9 and see how the planets look for yourself.  That mask will bring it down to an f/9.2 instrument so should tame a lot of the CA. 

 

 

Or a Televue Nagler 3-6 Zoom!

+1 for each of these . . .  Keep us posted, please . . . and maybe look into a field flatner for your f5.9 and use a Mask  too ???

 

Very Best Regards,

 

Ed (aka eblanken)


Edited by eblanken, 16 November 2020 - 10:12 PM.


#34 BillP

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Posted 16 November 2020 - 11:25 PM

I think I have those covered. A 5mm Pentax XO, a 6mm Supermono, and a 7mm Pentax SMC ortho.

Plus various Bak4 marbles from China waiting to be put in a housing and tested...
Just a bit worried about the old GP mount with that moment arm but we shall see.

Yes you do ... that's all best-produced planetary glass waytogo.gif


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#35 michiel

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Posted 17 November 2020 - 03:34 AM

You should make a 100mm mask for your current 152 f/5.9 and see how the planets look for yourself.  That mask will bring it down to an f/9.2 instrument so should tame a lot of the CA. 

Hi, ywah I did that and views were slightly better, compromise beteen less aperture and less CA.



#36 michiel

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Posted 17 November 2020 - 03:39 AM

Hi Michiel & All,

 

So much good advice here in this thread. I'd do the mask experiment first. And buy the 3mm-6mm TV Zoom next if that suits you  for the 152mm. And try some filters in the 152mm as well.

 

 

 

+1 for each of these . . .  Keep us posted, please . . . and maybe look into a field flatner for your f5.9 and use a Mask  too ???

 

Very Best Regards,

 

Ed (aka eblanken)

Hi Ed, Yeah, I have the 3-6 televue and tried with masks and aperture stop. Thanks everybody for the remarks. Indeed my head says... better buy a 8 inch f6 planetary newton for the same price.... but a long refractor is da bomb


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#37 25585

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Posted 17 November 2020 - 04:44 AM

Whether a telescope of any given size is enough for serious observing depends more on the observer than the aperture... 

 

 

Clear skies!

Thomas, Denmark

Aperture can make seeing some things easier though. Its like everyone has their own display settings preferences on TV sets, devices etc. 



#38 Jon Isaacs

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Posted 17 November 2020 - 06:15 AM

Aperture can make seeing some things easier though. Its like everyone has their own display settings preferences on TV sets, devices etc. 

 

Hopefully no one doubts the value of increased aperture in showing more planetary detail. Fine scale contrast transfer depends on aperture, image brightness and resolution are also functions of aperture.  With aperture, comes a variety of liabilities.

 

 

If I compare the planetary detail I see in my 102 inch apo, 120 mm ED, my 10 inch and 13.1 inch reflectors, it directly corresponds to the aperture.  Granted I live very the coast in the south west corner of the continental US in a very mild climate that's normally south of the jet streams..

 

Regardless, "serious planetary observing" can be done with all four scopes just as casual planetary observing can be done with all four scopes. In my mind, "serious observing" is an attitude on the part of the observer, a dedication to patience and perseverance.. it's really about being the best observer one can be, regardless of one's equipment.

 

If a 4 inch is not sufficient for serious observing of the planets, what is enough? A 6 inch is only somewhat better.  A 10 inch is only somewhat better than that...

 

There's enough to see in a 4 inch to keep one busy...

 

Jon


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#39 michiel

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Posted 17 November 2020 - 06:26 AM

Yesss, I made a totally senseless decision and pulled the trigger for the 102mm F11 ED refractor at TS telescope  services. I am exited. I know that it is not a decision made with the head.... there are scopes around for the same or not substantially more money that will blow it away but hey, I like long refractors.  I see it as a little corona present.... working at home all the time, a man needs new toys now and then. lol.gif

smile.gif smile.gif smile.gif smile.gif


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#40 CHASLX200

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Posted 17 November 2020 - 06:47 AM

A 120mm is small enough to be easy to handle and not need a big mount.  One you get into the 150mm size you need a bigger and heavy mount. 7" and up we are talking much more money and a much bigger mount.  This is where the old school 8" F/8 Newt shines since it cost 30 times less than a 7 or 8" APO and is much more easy to handle and mount.


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#41 beanerds

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Posted 17 November 2020 - 07:02 AM

Whether a telescope of any given size is enough for serious observing depends more on the observer than the aperture... 

 

 

Clear skies!

Thomas, Denmark

Spot on mate .

 

About 15 years ago when I still had me C102 achromat after a good public night showing Saturn and the Moon to the public  my observing buddy who was driving the C14 all night in the observatory with me out on the observing platform with my C102 sitting on her Vixen SP on the pier , so after the public left we continued as Jupiter was rising .

 

FF to about 1am and Jupiter was about 70 degrees up , we were both totally dark adapted , 3 hours of silence and Jupiter .

 

The C14 was cruzeing at 400x , my C102 was doing well at 200x .

 

I  was jumping between the C14 and my 102  as was Terry and we slowly upped the magnification ,,, C14 600x  , C102  300x and because I knew where to look on Jupiter when coming from the C14  , we could both see the same features , not as detailed for sure but there for the offering , cool and easily but I would say without a C14 at 600x only  20 metres away it would have been hard but it goes to show the detail is there but you just have to know exactly  where to look .

 

Beanerds .


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#42 Mr. Mike

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Posted 17 November 2020 - 07:06 AM

A 120mm is small enough to be easy to handle and not need a big mount.  One you get into the 150mm size you need a bigger and heavy mount. 7" and up we are talking much more money and a much bigger mount.  This is where the old school 8" F/8 Newt shines since it cost 30 times less than a 7 or 8" APO and is much more easy to handle and mount.

Oh I believe a 120mm scope needs a pretty substantial mount.  If there is one thing that gets screwed up in this hobby, and most of us have been there, it’s having a scope that is under-mounted.  Nothing will wreck the view from your boutique refractor than a shaky or unstable mount/tripod combo. Just my take on it.

 

 As for a 4” and planets? I’ve had some enjoyable nights with my 4” on the planets.  Seeing and conditions are a huge part of this as has been mentioned by many already. The other night I had a great night even with the big planets(Saturn, Jupiter)planets being only midway up in the sky.  But, Mars was still iffy for me even though it was higher up.  Personally, in a perfect setup I’d probably have a larger scope if I was doing planets more seriously and often.  But they are only a minor part of my viewing pleasures.  I’m a cluster, brighter DSOs kind of guy.  


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#43 CHASLX200

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Posted 17 November 2020 - 07:13 AM

Oh I believe a 120mm scope needs a pretty substantial mount.  If there is one thing that gets screwed up in this hobby, and most of us have been there, it’s having a scope that is under-mounted.  Nothing will wreck the view from your boutique refractor than a shaky or unstable mount/tripod combo. Just my take on it.

 

 As for a 4” and planets? I’ve had some enjoyable nights with my 4” on the planets.  Seeing and conditions are a huge part of this as has been mentioned by many already. The other night I had a great night even with the big planets(Saturn, Jupiter)planets being only midway up in the sky.  But, Mars was still iffy for me even though it was higher up.  Personally, in a perfect setup I’d probably have a larger scope if I was doing planets more seriously and often.  But they are only a minor part of my viewing pleasures.  I’m a cluster, brighter DSOs kind of guy.  

A CG5 is fine for a 120 or even SP mount should hold it. But a 150mm needs a G11 or AP 800 or 900 mount.  For me anyways.  I like over mounted scopes.


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#44 Jon Isaacs

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Posted 17 November 2020 - 07:42 AM

Yesss, I made a totally senseless decision and pulled the trigger for the 102mm F11 ED refractor at TS telescope  services. I am exited. I know that it is not a decision made with the head.... there are scopes around for the same or not substantially more money that will blow it away but hey, I like long refractors.  I see it as a little corona present.... working at home all the time, a man needs new toys now and then. lol.gif

smile.gif smile.gif smile.gif smile.gif

 

:waytogo:

 

I think you made a very sensible decision... you're going to have a lot of fun with your new scope.

 

Totally senseless:  I did a little research. There are McDonald's in the Netherlands. Instead of your fine new refractor, I calculate you could have bought about 120 Big Macs.

 

Yuck...

 

Jon


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#45 michiel

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Posted 17 November 2020 - 08:11 AM

waytogo.gif

 

I think you made a very sensible decision... you're going to have a lot of fun with your new scope.

 

Totally senseless:  I did a little research. There are McDonald's in the Netherlands. Instead of your fine new refractor, I calculate you could have bought about 120 Big Macs.

 

Yuck...

 

Jon

Thanks Jon, bawling.gif I want my big Mac......     smile.gif


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#46 dweller25

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Posted 17 November 2020 - 08:21 AM

Good choice Michiel,

I have been using a 4” F/8 refractor to sketch Mars recently - you can see my drawings in the sketching section. 
Average seeing (ever present jetstream) affects my views so hopefully you will see a little more smile.gif

I do find that binoviewers allow planetary detail to be seen easier waytogo.gif


Edited by dweller25, 17 November 2020 - 08:24 AM.


#47 25585

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Posted 17 November 2020 - 11:56 AM

waytogo.gif

 

I think you made a very sensible decision... you're going to have a lot of fun with your new scope.

 

Totally senseless:  I did a little research. There are McDonald's in the Netherlands. Instead of your fine new refractor, I calculate you could have bought about 120 Big Macs.

 

Yuck...

 

Jon

Overpriced artery clogging junk food. 4" F11 refractor, even ED, must be very CA free, & lasts a lifetime.  



#48 25585

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Posted 17 November 2020 - 12:01 PM

Oh I believe a 120mm scope needs a pretty substantial mount.  If there is one thing that gets screwed up in this hobby, and most of us have been there, it’s having a scope that is under-mounted.  Nothing will wreck the view from your boutique refractor than a shaky or unstable mount/tripod combo. Just my take on it.

 

 As for a 4” and planets? I’ve had some enjoyable nights with my 4” on the planets.  Seeing and conditions are a huge part of this as has been mentioned by many already. The other night I had a great night even with the big planets(Saturn, Jupiter)planets being only midway up in the sky.  But, Mars was still iffy for me even though it was higher up.  Personally, in a perfect setup I’d probably have a larger scope if I was doing planets more seriously and often.  But they are only a minor part of my viewing pleasures.  I’m a cluster, brighter DSOs kind of guy.  

The higher magnification you can go, the better mount and tripod you need. I have the 'pod, an EQ6, but not yet decided on a mount, DSC or GOTO, or neither.


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#49 25585

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Posted 17 November 2020 - 12:04 PM

A 120mm is small enough to be easy to handle and not need a big mount.  One you get into the 150mm size you need a bigger and heavy mount. 7" and up we are talking much more money and a much bigger mount.  This is where the old school 8" F/8 Newt shines since it cost 30 times less than a 7 or 8" APO and is much more easy to handle and mount.

I wish they were still made, but my 10" F6 is very good.


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#50 BillP

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Posted 17 November 2020 - 12:08 PM

Yesss, I made a totally senseless decision and pulled the trigger for the 102mm F11 ED refractor at TS telescope  services. I am exited.

This looks to be quite a nice scope! 

  • Good looking R&P focuser with fine focus
  • Retractable dew shield
  • Collimatable cell
  • Binoviewer friendly so no need for a OCA/GPC
  • Should be little to no CA if as they say equivalent to a FPL-53 f/8 doublet
  • Long focal length means any eyepiece new or old will work like a champ in it (this in itself is wonderful), and
  • Even though long focal length with something like a 40XW you will get a generous 2.3 deg TFOV

Congrats! waytogo.gif  You are going to have a lot of celestial adventures with this scope!!


Edited by BillP, 17 November 2020 - 12:10 PM.

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