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Planets with a Reflector

Planet SCT Reflector Visual
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#76 Nightskyman

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Posted 15 December 2022 - 11:12 PM

Thanks for the help and the image of the various parts of the view is great, it is the best with explanations and makes complete sense! One last question, how can I tell or verify if the secondary mirror is centered under the draw tube?



#77 Sky Muse

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Posted 15 December 2022 - 11:15 PM

Thanks for the help and the image of the various parts of the view is great, it is the best with explanations and makes complete sense! One last question, how can I tell or verify if the secondary mirror is centered under the draw tube?

Again, with the cross-hairs of your Cheshire...

 

pie slices2.jpg

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#78 Nightskyman

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Posted 19 December 2022 - 10:16 PM

When initially locating a planet, what is the suggested lens size to use first and what is the procedure to find or get to the best eyepiece for that evening ? I am using an 8” dob



#79 Sky Muse

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Posted 20 December 2022 - 03:18 PM

I use a 32mm Plossl to locate an object, then I swap that out with a 6mm or other for a closer look.  If a 6mm is too close, or blurry or soft, try an 8mm or longer.



#80 TayM57

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Posted 20 December 2022 - 03:34 PM

An 8-inch Dob is superb for viewing the planets, assuming that the collimation is spot-on and it's well cooled.

 

On mediocre to average nights 120X is a good magnification. On better nights, you can usefully go as high as 180X. On truly outstanding nights you might benefit from 240X.

 

Specific brands don't really matter; they're kinda all the same, as far as I'm concerned. The most important considerations are eye relief and apparent field of view.

And patience, in spades. For planetary, I find that sitting for long extended periods of time to catch the moments of great seeing is a treat. So I would say patience is one of the most important aspects of observing, particularly with regards to planets/lunar.


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#81 Nightskyman

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Posted 20 December 2022 - 04:49 PM

I struggle with assessing the seeing on any given night. Sometimes, while the sky looks clear, I don’t always get the best image. As a beginner, I’m not quite sure how to distinguish between a good seeing night versus collimation being off. Having uploaded a photo of my collimation, Vic Meanard says it is good enough for starting so I am assuming it must be the seeing. I am also struggling a bit with getting the object in my eyepiece field of view. The eye relief is between 15mm up to 22mm depending on the size. The  field of view is 66 degrees for my 6 and 9mm and is 52degrees for my 25 and 32mm. I am primarily working with Jupiter as it is an easy target to get used to using my new telescope. I use an 8 inch Dobsonion with StarSense Explorer and I’m finding that, it sometimes struggles finding its location and once it does, as you move it it tends to lose its location fairly easily. The location of the red dot finder, even though I believe I have aligned it correctly, causes a very awkward position to bend and use it.  I am thinking of buying a Orion dual finder scope mount so as to move the red dot finder out a bit into a better position on the one  and possibly adding a focal finder scope to the other  with crosshairs as well.



#82 AbstractGeo

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Posted 23 December 2022 - 09:34 AM

As a beginner, I’m not quite sure how to distinguish between a good seeing night versus collimation being off. 

In my very limited understanding, a good place to start is "how much are the stars visibly twinkling to the naked eye?"

 

In my understanding, assuming the scope is sitting still, if your images are blurry-but-stable, you probably have an optical issue (focus, collimation, bad optics, or even too much magnification). If everything is swimming around, wiggling, etc, you have either:

  • Bad seeing
  • A telescope that hasn't cooled properly / reached thermal equilibrium

Don't underestimate that second one; leaving my GSO 8" solid-tube dobsonian (very similar to yours) outside with the fan on for a half hour made worlds of difference when viewing on a moderately cold night (maybe 40 F /4.5 C) here in the northeastern US. I pointed the scope at a star and took it out of focus, and the circle of light was visibly wiggly-as-heck, like looking into a disturbed pond.

 

I'm a beginner, so, please take all of this with a grain of salt! But, if it's a-swimin', it's probably bad seein'.


Edited by AbstractGeo, 23 December 2022 - 09:34 AM.

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#83 gene 4181

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Posted 23 December 2022 - 10:07 AM

I struggle with assessing the seeing on any given night. Sometimes, while the sky looks clear, I don’t always get the best image. As a beginner, I’m not quite sure how to distinguish between a good seeing night versus collimation being off. Having uploaded a photo of my collimation, Vic Meanard says it is good enough for starting so I am assuming it must be the seeing. I am also struggling a bit with getting the object in my eyepiece field of view. The eye relief is between 15mm up to 22mm depending on the size. The  field of view is 66 degrees for my 6 and 9mm and is 52degrees for my 25 and 32mm. I am primarily working with Jupiter as it is an easy target to get used to using my new telescope. I use an 8 inch Dobsonion with StarSense Explorer and I’m finding that, it sometimes struggles finding its location and once it does, as you move it it tends to lose its location fairly easily. The location of the red dot finder, even though I believe I have aligned it correctly, causes a very awkward position to bend and use it.  I am thinking of buying a Orion dual finder scope mount so as to move the red dot finder out a bit into a better position on the one  and possibly adding a focal finder scope to the other  with crosshairs as well.

 With practice  tracking the planets and everything else becomes second nature.   You'll know good seeing when you see it .  Get good tools too collimate with  and they'll pay you back with excellent views when the seeing cooperates.   When you get a single little diffraction  ring around a star or  Jupiters moons, thats good seeing . Normally Jupiter's moons look like those pinwheels we taped to the bike handlebars ,  check out ,  Damian Peach's  Pickering Scales of Seeing .



#84 gene 4181

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Posted 23 December 2022 - 10:18 AM

 Getting the dob out  an hour before viewing with a small box fan blowing on the  back don't hurt.  2 hours without the fan ,   almost 2 hours for a 150 mak . The little 6inch f5 takes about 30 minutes to an hour IF its real cold.  Pennsylvania , are you up on a hill or in a valley ?  Downwind of  hills / mountains, in the lee  makes for turbulent air,  down in a valley  and the cold air settles down into it. Jupiter is best right before  / at dusk as soon as  you can pick it out of a blue sky .  Cap your scope and bag the mirror end before bringing it in, once in  cover it with a blanket and  store it  horizontally  . Parabolas are little bowls, don't want too pool water in the mirror .  Keeping as much cold  DRY air in the tube  and letting it come to equilibrium slowly is a good thing. (Works for ALL scopes).  smile.gif



#85 Anony

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Posted 23 December 2022 - 11:54 AM

I struggle with assessing the seeing on any given night. Sometimes, while the sky looks clear, I don’t always get the best image. As a beginner, I’m not quite sure how to distinguish between a good seeing night versus collimation being off. Having uploaded a photo of my collimation, Vic Meanard says it is good enough for starting so I am assuming it must be the seeing. I am also struggling a bit with getting the object in my eyepiece field of view. The eye relief is between 15mm up to 22mm depending on the size. The  field of view is 66 degrees for my 6 and 9mm and is 52degrees for my 25 and 32mm. I am primarily working with Jupiter as it is an easy target to get used to using my new telescope. I use an 8 inch Dobsonion with StarSense Explorer and I’m finding that, it sometimes struggles finding its location and once it does, as you move it it tends to lose its location fairly easily. The location of the red dot finder, even though I believe I have aligned it correctly, causes a very awkward position to bend and use it.  I am thinking of buying a Orion dual finder scope mount so as to move the red dot finder out a bit into a better position on the one  and possibly adding a focal finder scope to the other  with crosshairs as well.

I guess one way to test is simply... how do other targets look?

 

Orion nebula, all nice and nebulous? Moon (when it's out)... nice and cratery? Are the stars sharp? You can do the star test, see how concentric they are.

 

If everything but Jupiter looks great, then it's probably just not a good night to view the planets.

 

And yes, a red dot finder with a dob can be problematic for the neck.  Maybe a Telrad or Quikfinder would be an option for you.

 

Although on my starsense scope I usually find it spot-on (or at least close enough). So it shouldn't be an issue finding major targets.

 

Typically I'd go with a 32mm to find a target, then move to a 9mm... and if the night agrees, go to 6 (or use my zoom). A 32mm plossl should be fine as far as getting Jupiter into your fov.


Edited by Anony, 23 December 2022 - 11:56 AM.


#86 Nightskyman

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Posted 23 December 2022 - 12:37 PM

Would an 8x50 right angle finder scope be worthwhile to more easily access / view from a more comfortable position.



#87 Anony

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Posted 23 December 2022 - 12:50 PM

Would an 8x50 right angle finder scope be worthwhile to more easily access / view from a more comfortable position.

Definitely more comfortable. I have one. Although they can be pricey (at least for a cheapskate like me). The only reason I have one is that it came with my scope.

 

But I think my brain is wired for red dots... either that, or my skies are so terrible that even with a right angle scope I have a problem finding targets using it. Or I should say some targets... easy things like the planets or orion nebula and so on I can usually aim without using a finder.

 

What I ended up doing was moving over a larger starpointer pro from a cheapo refractor I bought ($50). It's not quite a telrad, but it does the circle thing and is larger than a typical red dot ... I wouldn't recommend it over a telrad or quikfinder, but for me it was like free, so figured I might as well move it over.  Depending on how bendable your neck is, a telrad or quikfinder may be another option for you -- I can't say which you'd prefer, everyone is different there. But to me,  RACI is fine, but not as helpful as a red dot (or red circle) finder.

 

If you have the holder thingies, I'd guess a RACI + Telrad/quikfinder would cover all of your bases. But you already have starsense, so it may be getting crowded up there.

 

Maybe practice a bit more with starsense? I also have a starsense SCT ... I find it pretty accurate and I am using it on slower scope than yours. Key is to use the 32mm plossl as your finder eyepiece.


Edited by Anony, 23 December 2022 - 12:56 PM.


#88 No N in collimation

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Posted 23 December 2022 - 01:39 PM

At one point I took the plunge and got a 4-element 2x Barlow thinking I would try it out. I don't know the first thing about optics, but the difference was striking. It now goes wherever I go. 

 

For planets I bought a Mak and some "edge-on" EPs. That's more money, but the views are really nice. 



#89 AbstractGeo

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Posted 23 December 2022 - 02:00 PM

I'll second the Telrad; it's hard to explain just how helpful that is, especially considering that star charts and such have "telrad cirles" often.

I wish could explain better how it works, but it's very much "just look along the length of your scope, even with both eyes open (for most people), and aim your scope until the magic red circle is where you want it."


Edited by AbstractGeo, 23 December 2022 - 02:00 PM.


#90 Nightskyman

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Posted 23 December 2022 - 06:01 PM

 All right, I’m not sure if this is the right forum for this question, but since it came up now, I’ll ask. As I mentioned above, my Starsense explorer 8 inch Dobsonian comes with a red dot finder. Its location is extremely difficult for use on this scope. I’m supposing its location is because of the Starsense explorer hardware mounted on top. so if I’m looking to add something else to make it easier, it seems like my main options would be either a RACI finder scope, a Telrad, or maybe even using a dual mounting bracket like one from Orion and then using two different methods. The last option seems a bit overkill.  I’m looking for any input that anyone has in regards to the different options with finder scopes, your experience with them, and the pros and cons? 



#91 Anony

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Posted 24 December 2022 - 12:58 PM

 All right, I’m not sure if this is the right forum for this question, but since it came up now, I’ll ask. As I mentioned above, my Starsense explorer 8 inch Dobsonian comes with a red dot finder. Its location is extremely difficult for use on this scope. I’m supposing its location is because of the Starsense explorer hardware mounted on top. so if I’m looking to add something else to make it easier, it seems like my main options would be either a RACI finder scope, a Telrad, or maybe even using a dual mounting bracket like one from Orion and then using two different methods. The last option seems a bit overkill.  I’m looking for any input that anyone has in regards to the different options with finder scopes, your experience with them, and the pros and cons? 

Not to complicate matters, but there is also a Rigel Quikfinder that you can add to your option list too. It's Telrad-ish, but not as bulky and there are some differences.

 

Afraid I don't own one, so others would have to chime in on it. You can check out youtube though and look at the comparisons there.

 

Maybe if you have a local club, someone there will own a RACI/Telrad/Quikfinder and you can test them out and see which you like best?


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#92 Nightskyman

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Posted 08 January 2023 - 04:44 AM

When is the best time for the best view of Venus and what to expect?



#93 mikemarotta

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Posted 08 January 2023 - 09:30 AM

When is the best time for the best view of Venus and what to expect?

Right now! It is high in the sky at sunset.

If you have a Moon filter, you will want to use it to help see the phase of Venus because the planet is very bright.

 

Good luck.

Mike M.



#94 CHASLX200

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Posted 08 January 2023 - 12:11 PM

When is the best time for the best view of Venus and what to expect?

Best before dark and when it is very close to us in a half phase or less. Not gonna see any detail other than a phase like the moon.



#95 star acres

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Posted 08 January 2023 - 08:29 PM

Sbony red band eyepiece. 5 or 6 wide glass lenses in a big aluminum case. s-l400 (1).jpg s-l400.jpg


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#96 Nightskyman

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Posted 08 January 2023 - 10:48 PM

Along with my 8” dob, my eyepieces are a 25mm plossl that came with my scope, 6mm and 9mm Agena Enhaced Wide Angle, a 32 mm Meade super Plossl, a Orion high power 2x 4 element Barlow, and a Celestron 8mm-24mm zoom. All 1.25 size. When I eventually add a upgraded eye piece wether it is a new size or upgrading a current size, what would you recommend for the 1st upgrade?



#97 Chad7531

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Posted 10 January 2023 - 06:16 AM

Along with my 8” dob, my eyepieces are a 25mm plossl that came with my scope, 6mm and 9mm Agena Enhaced Wide Angle, a 32 mm Meade super Plossl, a Orion high power 2x 4 element Barlow, and a Celestron 8mm-24mm zoom. All 1.25 size. When I eventually add a upgraded eye piece wether it is a new size or upgrading a current size, what would you recommend for the 1st upgrade?


I would probably start with a 12-15mm for a 2-2.5mm exit pupil, that’s my sweet spot for DSOs. Or are you looking for a high power planetary piece?

#98 Nightskyman

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Posted 10 January 2023 - 10:04 AM

Didn’t have anything particular in mind just a general question although wondering what brand and line would be a good choice for a step up from entry level?



#99 Nightskyman

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Posted 10 January 2023 - 10:28 AM

What size eyepiece is typically used for initially locating the object? Depending upon the object, what size range would typically be used?



#100 rhetfield

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Posted 10 January 2023 - 10:36 AM

When initially locating a planet, what is the suggested lens size to use first and what is the procedure to find or get to the best eyepiece for that evening ? I am using an 8” dob

You generally would start out with a low power so that you are seeing a wide angle view to make it easier to find the planet, then go to as high of power of eyepiece as will show the planet decently.  That will vary from night to night.  If it is a bright planet and you have a well enough aligned finder on the scope, you might be able to start with a higher power eyepiece.  My finder is well aligned and I can normally get a planet into the 0.5 deg FOV of my 144x 4.5mm eyepiece.  Add a barlow and I can't.


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