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Recommendations for beginner with Astroscan?

Eyepieces Planet Observing Beginner
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#76 Ryanocalypse

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Posted 12 April 2021 - 06:29 AM

I have owned an Astrscan for over 30 years. It has flown with me to many vacation destinations in an airliner overhead compartment. I truly have an emotional attachment to it.

But, as has been pointed out by some previous posters, do no expect much from planets. My husband and I recently took the Cherry Bomb apart to clean and collimate it. This was an ordeal.

Expand your deep sky object list though. Yesterday, one of my observing friends said he saw all parts of the Veil Nebula near Cygnus in one eyepiece view with an Astroscan. This was in south no-light-pollution Texas, but still.

Regarding the 28mm RKE: guard it with your life! An awesome eyepiece.

Thank you for some insight into your Cherry Bomb, as you call it! The Astroscan really is a unique scope. When I first saw it in person, I thought how wild the shape was, that it just wobbles back and forth on the stand like a floating ball. It doesn't tip over and is very user friendly, honestly much bigger than I thought it would be as well! That's amazing your friend was able to see the Veil Nebula! That must have taken some skill actually finding it on the Astroscan, even in the dark skies. I can barely see the Orion Nebula and Andromeda Galaxy from where I am. They both appear as a very slight, dim cloud, but wow what an amazing sight! My wife and I camped in the Utah wilderness last year and I would have loved to have my Astroscan at that time. I will never get rid of these RKE eyepieces, the 28mm is perfect for the Astroscan too. Thank you again!

 

- Ryan



#77 gnowellsct

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Posted 12 April 2021 - 07:07 AM

You could try ski wax pick it up from Dick's sporting goods or order it online. I use it to help the legs on my wooden tripod retract and extend.

The r k e eyepieces are keepers, hang on to them when if you trade up as they're always seems to be a use for an RKE even when you have an eyepiece collection worth thousands of dollars.

This telescope was designed back in the 1950s or 1960s. Back then things like powermates didn't exist. You will quickly learn that as you upgrade certain elements of this system you overwhelm others. Among the problems is that a powermate would be too heavy. I would also be surprised if a powermate fit at all it is a 2-in eyepiece and the default on this era telescope is 1.25 in.

One of the things to do is open yourself up mentally to the idea that a large part of what is going to happen here is not just lessons about the sky but lessons about system engineering and the relationship of design and engineering choices to cost and performance.

I spent $1,000 once upgrading a 1965 4.25 in f10 telescope. I could have bought a 12 in China import for that price. But I learned so much about telescope design that it was well worth the expenditure and at the end I had a pretty good newtonian that gives extremely sharp views. I mean I learned multiple lessons about the legs at the bottom of the pier, the construction of the pier, how the tracking of that era worked and what its limitations were; also balance, focuser, mirror cell, and so on.

The market is a great teacher in this. It allows you to make mistakes and still recover most of your money. An astronaut membership is one of the best investments I ever made. 15 bucks.

I would advise you to use that astroscan up to the point that some feature of it bothers you so much that you can't stand it and you have a better idea of what you want.

To close, understand what the astroscan does. By shortening the length of the mirror it solves an important problem of telescope use: mechanical instability. It is heavily built in the butt and is very short so the leverage instability is minimized in the wind and when you change eye pieces. It has no tracking so the setup is very simple and a long set up time does not discourage you from popping up to get a view.

To get these things the designers shortened the focal ratio of the mirror to the point where optical performance is compromised on planets. They did this at a time when fast mirrors, unlike those today, were not routinely made to high performance standards. Because the short focal length and lack of tracking will tend to reduce the time that most users want to look at planets, the focuser doesn't need to fine adjustment that is really necessary to make a fast telescope easy to use.

It is not an easy telescope to collimate because it is not expected that the users will be bothering with this complication. This goes to achieving fast set up time, ease of use, and the all important stability. And all these things solve the extremely frustrating user problem of a telescope that, the instant you let go to change an eyepiece or invite someone else to view, moves itself away from the object so you have to find it again.

Within its limitations it's a brilliant design. It has been good enough to lead generations of users to more expensive, higher performing instruments. And you'll notice that experienced users who have long since moved on rarely speak ill of it.

Greg N
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#78 noisejammer

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Posted 12 April 2021 - 07:10 AM

Thank you Bruce! Would it still be impossible to achieve a focal length greater than 1° even with some of the eyepieces that offer extremely wide FOV, like the Naglers or Ethos? Not that I would get one immediately, I'm just curious. The C8 looks to be the older orange one. There is a finder but it's not orange like I would see on the older one, it also does come with the original mount. I read there was a time in the 80s when these scopes were mass produced and quality shot down, do you have any experience with this and if so, still believe it would be worth the $450? I would be happy with either scope, if they aren't sold already haha!

 

- Ryan

The limitation is in the design of the C8. The optical path is 38mm in diameter at the exit pupil of the scope. If you calculate 2 * atan (19/2048), you get 1.06°.

 

It is possible to achieve a field of about 1.1-1.15 degrees with some vignetting, but no more. It doesn't matter whether you use ultra-wide angle eyepieces or f/6.3 focal reducers or visit a witch doctor for a potion ... optics doesn't seem to  care for magical thinking. :lol:

 

Some of the older Celestrons were a bit odd but - never having seen one - I suspect this is greatly exaggerated. Since it includes a mount I'd say go for it. I'd still get a better finder and - unless you have a triple jointed neck - you will need a diagonal.

 

As you say, either scope will be great.



#79 gnowellsct

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Posted 12 April 2021 - 07:18 AM

A 3.2 mm eyepiece used in any scope is pushing the limits. IMO, you would never get what I consider good views with it and your Astroscan. I would not go any shorter than 5 mm, and likely not use anything below 8 mm.

I usually define the limit as an eyepiece focal length that is one half the telescope focal ratio. But to do that you're getting into the precision instrument in good seeing category.

And a telescope with a narrow field from a 60° or less eye piece a 3.2 mm eyepiece is certainly asking for a frustrating experience.

A 3.2 mm on one of your better refractors mounted on a stable mount with tracking is pretty routine for many users. I use my 3.5 mm xw quite often.

But with this optic and this mounting system in this price range I think you are absolutely correct. I raise the point because newcomers might incorrectly conclude that a 3.2 or 3.5 mm eyepiece has no practical use. That is not true. But it is true for the large majority of inexpensive entry level instruments, so it certainly is true enough.

Edited by gnowellsct, 12 April 2021 - 10:21 AM.

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#80 gnowellsct

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Posted 12 April 2021 - 07:26 AM

If you ” barely can see ” M42 or the Andromeda Galaxy you are probably trying to do it while the Moon is up or from a light polluted Urban environment.

This is where we get to the sad truth that one of the best tools for astronomy is a functional car and the time to drive somewhere and a remote site where you won't get chased away by an angry farmer with a 12 gauge.
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#81 Ryanocalypse

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Posted 12 April 2021 - 07:31 AM

If you ” barely can see ” M42 or the Andromeda Galaxy you are probably trying to do it while the Moon is up or from a light polluted Urban environment.

This is where we get to the sad truth that one of the best tools for astronomy is a functional car and the time to drive somewhere and a remote site where you won't get chased away by an angry farmer with a 12 gauge.

Yes, unfortunately I am near Nashville and light pollution can be pretty bad. There are some darker skies towards recreational areas but the convenience is missing. I'm moving to northern Montana this summer and cannot wait for the dark skies over there!

 

- Ryan



#82 Ryanocalypse

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Posted 12 April 2021 - 07:39 AM

The limitation is in the design of the C8. The optical path is 38mm in diameter at the exit pupil of the scope. If you calculate 2 * atan (19/2048), you get 1.06°.

 

It is possible to achieve a field of about 1.1-1.15 degrees with some vignetting, but no more. It doesn't matter whether you use ultra-wide angle eyepieces or f/6.3 focal reducers or visit a witch doctor for a potion ... optics doesn't seem to  care for magical thinking. lol.gif

 

Some of the older Celestrons were a bit odd but - never having seen one - I suspect this is greatly exaggerated. Since it includes a mount I'd say go for it. I'd still get a better finder and - unless you have a triple jointed neck - you will need a diagonal.

 

As you say, either scope will be great.

Thank you for the input Bruce! Your math sounds like you are experienced to make me trust you, as I think I understood about half of what you said haha! I'll be doing more research and reading up on this before I get any more eyepieces, my RKEs will do perfectly well right now. I'm going to go with this XT8, I still have much to learn before trying to get into SCTs and other scopes C8, as it seems like a great opportunity that would be difficult to pass up. I also think you underestimate my giraffe neck!

 

- Ryan


Edited by Ryanocalypse, 12 April 2021 - 04:44 PM.


#83 Dave Mitsky

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Posted 12 April 2021 - 11:45 AM

Thank you for some insight into your Cherry Bomb, as you call it! The Astroscan really is a unique scope. When I first saw it in person, I thought how wild the shape was, that it just wobbles back and forth on the stand like a floating ball. It doesn't tip over and is very user friendly, honestly much bigger than I thought it would be as well! That's amazing your friend was able to see the Veil Nebula! That must have taken some skill actually finding it on the Astroscan, even in the dark skies. I can barely see the Orion Nebula and Andromeda Galaxy from where I am. They both appear as a very slight, dim cloud, but wow what an amazing sight! My wife and I camped in the Utah wilderness last year and I would have loved to have my Astroscan at that time. I will never get rid of these RKE eyepieces, the 28mm is perfect for the Astroscan too. Thank you again!

 

- Ryan

The 28mm RKE is renowned for the "floating in space" effect that it produces.



#84 SteveG

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Posted 12 April 2021 - 04:33 PM

Thank you for the input Bruce! Your math sounds like you are experienced to make me trust you, as I think I understood about half of what you said haha! I'll be doing more research and reading up on this before I get any more eyepieces, my RKEs will do perfectly well right now. I'm most likely going to go with this C8, as it seems like a great opportunity that would be difficult to pass up. I also think you underestimate my giraffe neck!

 

- Ryan

Except for it not being on a driven mount, the XT8 will do everything the C8 will do, only better. The C8 cannot produce flat, wide fields, which the XT8 can excel at.

 

Is there dew where you live? If so, the C8 will be covered in dew, requiring either a heater, dew shield, or perhaps insulation. No worries at all with the XT8 and dew.



#85 Mitrovarr

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Posted 12 April 2021 - 04:41 PM

No worries about dew except for the finder and/or telrad and all your eyepieces.
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#86 Ryanocalypse

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Posted 12 April 2021 - 04:42 PM

Except for it not being on a driven mount, the XT8 will do everything the C8 will do, only better. The C8 cannot produce flat, wide fields, which the XT8 can excel at.

 

Is there dew where you live? If so, the C8 will be covered in dew, requiring either a heater, dew shield, or perhaps insulation. No worries at all with the XT8 and dew.

Hey Steve, thank you for the heads up! I actually decided earlier that I was going with the XT8, I forgot to give an update. When trying to figure out what year the C8 was from, I realized I was out of my comfort zone when it came to SCTs. I'd like to learn more about the models and components before jumping into one for my next scope. I wont have a driven mount so you're right, the Dobsonian will be much user friendly and produce great images. I'll be picking up the XT8 in mid-May. I appreciate you looking out!

 

Thank you also to everybody that has helped out in my time of internal struggling! You all have boosted my confidence and given me the opportunity to learn and experience through my own decisions. I appreciate everybody's feedback and recommendations for my Astroscan. Since I'll be getting a Dobsonian, I'm not going to purchase a high powered Paradigm eyepiece but will likely get a Barlow soon. I still learned a lot about the eyepieces and limits of certain scopes from all of your experiences. I'm going to focus my Astroscan on what everybody has recommended and what got me loving the scope, wide scans of the sky. 

 

- Ryan


Edited by Ryanocalypse, 12 April 2021 - 04:51 PM.

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