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Looking for advice on my next purchase for 8" SCT

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#1 FerrariMX5

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Posted 05 June 2020 - 01:23 PM

I have:

a nexstar 8

a 12.5mm (1.25)

a 32mm (1.25 GSO Plossl).

a need for magnification beyond the 12.5mm

 

Used the telescope three times.

Once with the 12.5 (Found the moon), but could not find the stars.

Ordered the 32mm, found Saturn, Jupiter and quite a few stars, magnified the planets to 160 times, (using the 12.5mm).

Sharp, Great definition of rings..    160X is still small, did not see the moons circling either planet..

 

I am thinking I need an 8mm (But need advice before I order).

Was also thinking of a midrange 18mm (But, probably will always start with the 32mm then jump to 12.5, therefore this may very well be a waste).

 

Would I be better served with a 7mm?   

How about a 6mm?

 

Yes, it is all about Saturn right now, and perhaps a crater or two on the moon.

 

Just starting out, vintage N8, but it works like a charm.  (Circa 2002)

 

(Also, just got the star pointer and it really does work well)

 

 

Tony


Edited by FerrariMX5, 05 June 2020 - 01:30 PM.


#2 rustynpp

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Posted 05 June 2020 - 01:33 PM

Waddup Tony! Welcome to CN.

 

An 8mm EP would be about 250x - perhaps a little too high for most nights. I'm not sure how familiar you are with the concept of "seeing," which is simply the degree to which turbulence in the atmosphere affects the fidelity of the image, but depending on your local conditions, you may find that 250x is a blurry mess on most nights because the "seeing" isn't steady enough. Same goes for 6 & 7mm EPs, naturally.

 

If I were in your shoes I would be looking for a 10mm EP, providing around 200x, before picking up any higher-mag EPs. The image will be smaller than it would be at 250x, but likely much sharper (on the majority of nights).

 

Regardless of the focal length you choose for your next EP, you should provide a budget you have in mind. Also, does your mount have tracking? If so, you can get away with EPs that have a small apparent field of view, but if not you may want to spend a bit more to get a widefield EP.

 

Cheers,

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#3 jmorales21

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Posted 05 June 2020 - 02:27 PM

I am curious about what you say that you were not able to see the satellites of Saturn or Jupiter. Jupiter's can be seen easily even with binoculars, so I am wondering if you got your focus sharp enough to see atmospheric details or just saw a blob. Same with Saturn, although its moons are significantly dimmer, some are well within the range of a Nextar 8 with a 32mm eyepiece. Can you describe what you saw?



#4 Mike W

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Posted 05 June 2020 - 02:45 PM

As you get higher in mag. your eyepieces need to be closer together, for instance my range at 880mm fl.is.

24- 19-14-10-8-6-5

36x,46x,62x,88x,110x,146x,176x

 

I would go for an 11or10mm


Edited by Mike W, 05 June 2020 - 02:47 PM.

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#5 FerrariMX5

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Posted 05 June 2020 - 05:45 PM

 

 Jupiter's moons can be seen easily even with binoculars, so I am wondering if you got your focus sharp enough to see atmospheric details or just saw a blob.  Can you describe what you saw?

 

jmorales21,

 

Gladly,

 

Saturn, although small using a 12.5mm, had well defined rings.

Jupiter might have had well defined moons that I thought were stars beyond the planet.

 

Both planets were bright and easily identified.

Impressively sharp, although Jupiter could well be described as having a softer, gas like surface at 160 times magnification.

 

Jupiter's cloud belts were clearly defined, albeit the planet was still viewed as being smaller than what I felt the telescope could easily handle last night. 

 

I should have counted the moons and at one point (Because I thought they were stars in the distance behind Jupiter) I was tempted to observe them for another 10 minutes to watch Jupiter hide the stars as it slowly blocked their view.

Had I done so, I may have realized they were moons and would have probably counted them. 

 

Tonight it will be cloudy, so my timing was bad and an opportunity was missed. 

 

I'm still having trouble aligning the stars to calibrate the Nexstar 8, but I am definitely getting better at it.

Perhaps I've been picking the wrong star when it slews to a section of stars, but that is for another thread.   

 

Last night showed me the capabilities of the 8" SCT. 

 

On the internet, there are much bigger pictures of the planets, so maybe it is time to enter into Astrophotography. 

 

On a side note:  I do have an over processed shot of the moon, taken on Passover with a Canon 7DMii and a 400 Prime "L" series 5.6.  (you could view that in the gallery) 

 

Using the 8" SCT as a 2032mm lens might be interesting. 

 

But, back to eye pieces, I am thinking now, perhaps a 10mm or possibly making the jump to the 8mm   ..   

 

taking baby steps..

 

Tony 

 

PS.   Had pretty much the same moon experience with Saturn, wish I had known..


Edited by FerrariMX5, 05 June 2020 - 08:27 PM.


#6 adamckiewicz

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Posted 05 June 2020 - 06:09 PM

I have a 12mm Ned 60’ and a morpheus 9mm with c8. And a 25mm plossl. 12mm is nice even with médium seeing, 9mm often usable. I have a 5mm also which I use only when the seeing is realy good. It’s nice whith Mars !
9mm is often usable but 12mm gives quite a nice view with c8!
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#7 Mike W

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Posted 06 June 2020 - 12:19 PM

jmorales21,

 

Gladly,

 

Saturn, although small using a 12.5mm, had well defined rings.

Jupiter might have had well defined moons that I thought were stars beyond the planet.

 

Both planets were bright and easily identified.

Impressively sharp, although Jupiter could well be described as having a softer, gas like surface at 160 times magnification.

 

Jupiter's cloud belts were clearly defined, albeit the planet was still viewed as being smaller than what I felt the telescope could easily handle last night. 

 

I should have counted the moons and at one point (Because I thought they were stars in the distance behind Jupiter) I was tempted to observe them for another 10 minutes to watch Jupiter hide the stars as it slowly blocked their view.

Had I done so, I may have realized they were moons and would have probably counted them. 

 

Tonight it will be cloudy, so my timing was bad and an opportunity was missed. 

 

I'm still having trouble aligning the stars to calibrate the Nexstar 8, but I am definitely getting better at it.

Perhaps I've been picking the wrong star when it slews to a section of stars, but that is for another thread.   

 

Last night showed me the capabilities of the 8" SCT. 

 

On the internet, there are much bigger pictures of the planets, so maybe it is time to enter into Astrophotography. 

 

On a side note:  I do have an over processed shot of the moon, taken on Passover with a Canon 7DMii and a 400 Prime "L" series 5.6.  (you could view that in the gallery) 

 

Using the 8" SCT as a 2032mm lens might be interesting. 

 

But, back to eye pieces, I am thinking now, perhaps a 10mm or possibly making the jump to the 8mm   ..   

 

taking baby steps..

 

Tony 

 

PS.   Had pretty much the same moon experience with Saturn, wish I had known..

You'll regret jumping to an 8mm!


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#8 whizbang

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Posted 06 June 2020 - 10:39 PM

Mid range 20mm or 24mm


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#9 clang

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Posted 10 June 2020 - 07:20 AM

The Badger Zoom is my suggestion.   They are excellent performers in an SCT, especially from 8 to 20 mm.


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#10 roblindau

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Posted 10 June 2020 - 09:56 AM

Hi Tony,

 

one of my best investments for my SCT was a binoviewer. You can get a good quality binoviewer for around 250 $. I for myself have a William optics binoviewer and I'm quite happy.

 

Combined with some inexpensive eyepieces, e.g. Plossl or Paradigm, the observation of moon and planets is a pleasure, much better than with mono-viewing with only one eyepiece.

 

Robert


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#11 psyhiker

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Posted 12 June 2020 - 09:00 PM

I've had an 8 inch SCT since 1987: here is my 2 cents: I almost never can use an eyepiece below 14 mm, every time I try with my 9.7 I am disappointed, a big soupy mess.  I would the coolest addition I made to my scope was the celstron f6.3 reducer that widened and flattened the field.  Higher power than 14 mm belongs to refractors, in my experience   



#12 eblanken

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Posted 12 June 2020 - 11:56 PM

You'll regret jumping to an 8mm!

I agree, get a 10mm to have more power than your 12.5mm. Alternately, look on the used market for a Vixen 8-24mm zoom or a Televue 8-24mm "click-stop" zoom. They pair up well with 2032mm to get you "just the right power" for each evening's sky conditions. Usually my sky conditions only support 11mm or 10mm or 9mm and rarely 8mm. After you gain some experience with the zoom on your SCT at your location's sky conditions, you can always get fixed eyepieces (possibly better quality than the zoom) if you want.

 

As far as alignment stars, the zoom can help you with that also: Start with 24mm setting and roughly center the first star, then zoom in, refocus and recenter until you are very well centered, then back to 24mm and onto the next alignment star and repeat.

 

My $0.02,

 

Ed (aka eblanken)

 

P.S. Hint: Jupiter's moons are mostly lined up with his equatorial belts.

 

P.P.S. Tell us more about your 12.5mm eyepiece: Is it a plossl ? Brand ?


Edited by eblanken, 13 June 2020 - 12:17 AM.


#13 whizbang

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Posted 13 June 2020 - 08:04 AM

Tony,

 

Unless you are exclusively interested in small objects, planets, double stars, planetary nebula, you would be better served with mid range eyepieces.  Specifically, an Explore Scientific 20mm 68 degree or the Bresser 20mm 70 degree.

 

If you absolutely think you need more magnification, my sister and I both have the ES 9mm 62 degree.  It is a good performer and a good value.


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#14 whizbang

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Posted 13 June 2020 - 08:10 AM

I just played around with the Field of View Calculator at

 

http://astronomy.too.../field_of_view/

 

I like the Bresser 15mm and 20mm to compliment the 12.5 and 32mm plossls that you already have.


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#15 FerrariMX5

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Posted 13 June 2020 - 01:24 PM

I agree, get a 10mm to have more power than your 12.5mm. 

 

P.P.S. Tell us more about your 12.5mm eyepiece: Is it a plossl ? Brand ?

University Or. 12.5mm Multi Coated (The word Multi-Colored is in Green) 

Volcano or Cone Shaped Eyepiece  1.25"

Orthoscopic

Looks and feels high quality, but do not have a lot of experience to reference.

Made in Japan.

 

Saturn is sharp with great detail shown in the rings.

 

Tony


Edited by FerrariMX5, 13 June 2020 - 01:51 PM.

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#16 eblanken

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Posted 13 June 2020 - 09:02 PM

University Or. 12.5mm Multi Coated (The word Multi-Colored is in Green) 

Volcano or Cone Shaped Eyepiece  1.25"

Orthoscopic

Looks and feels high quality, but do not have a lot of experience to reference.

Made in Japan.

 

Saturn is sharp with great detail shown in the rings.

 

Tony

OK, good Tony,

 

Now we know why it worked well on Saturn and its rings. An Ortho is a good planetary eyepiece. It would not work well for me, but may work well for you because of the difference in our eyes. I wear eyeglasses to correct my 62 year old eyes. I have to wear them because of my eyes' astigmatism. My question to you is this, "Are you comfortable with using your 12.5mm Ortho ?" which leads to the next question, "Would a 10mm Ortho be OK even if your eye needed to be slightly closer to the eyepiece ?" then that question leads to "What about a 9mm Ortho ? with the necessity for an even closer "eye relief" needed ? How about an 8mm Ortho ?" and as you can see, the analysis continues until your eyes may or may not be "happy" with Orthos of smaller and smaller eye relief. Some people love Orthos and spend lots of money to eventually get a whole set. I'm not an Ortho guy, BECAUSE of MY eyes, not because they are bad, just bad FOR ME. I have learned that I'm a barlowed Plossl guy, which is kind of how the zooms work. Make sense ?

 

Cheers,

 

Ed


Edited by eblanken, 13 June 2020 - 09:06 PM.

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#17 eblanken

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Posted 13 June 2020 - 10:10 PM

Hi Tony & psyhiker,

 

I've had an 8 inch SCT since 1987: here is my 2 cents: I almost never can use an eyepiece below 14 mm, every time I try with my 9.7 I am disappointed, a big soupy mess.  I would the coolest addition I made to my scope was the celstron f6.3 reducer that widened and flattened the field.  Higher power than 14 mm belongs to refractors, in my experience   

 

One thing I would note is that one's local atmospheric conditions can make a HUGE difference in how high the magnification can be "pushed" with an 8 inch SCT. At home, in the greater Portland Oregon metro area, I have trouble with my SCT getting above 200 power, but at 5,000 feet up in the Cascade Mountains on a good night 250x is easily dooable AND on a great night, I can go higher.

 

I suspect that psyhiker having trouble with getting below 14mm may have something to do with local atmospheric conditions: Burbank, CA is quite different than Halfway up Mount Hood at 5,000 feet in cool, clear still air. Another thing that comes into play is the optics of the 8 inch SCT (not all SCTs are created equal) and the third thing that comes into play is collimation. From Tony's report on viewig Saturn in the 12.5mm Ortho, it is clear to me that atmospheric "seeing" and collimation were both working on that night for Tony and his SCT.

 

Speaking of collimation, Tony AND/OR psyhiker, you may want to get a small mm eyepiece for "touching up your SCT's collimation" on the best of your viewing nights in Niceville Florida. This may be a 2.5mm, 3.0mm or 4mm eyepiece that lets you look so closely into a star that you can make out the airy disk and diffraction rings that your SCT produces on a "Point Source" aka Star. As you "pump up the magnification" you get well past the point where you optics can work and into the realm where the airy disk lives. But that's another discussion for another time . . .

 

Best Regards,

 

Ed

 


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#18 PNW

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Posted 14 June 2020 - 12:50 AM

I, too, have a Nexstar 8 in the PacificNorthWest. I, too, wanted magnification, did the math and bought the 6.5mm. Its OK on the moon . I generally use my 40mm to locate an object. My 18mm and 12mm are the most used, depending on seeing and FOV I want. The 9mm is a test for seeing conditions. It makes things pop on good nights, but not every night. As for the 6.5....I had to buy an AR 127 and mount to make it useful...Barry

 

edit: My 20mm Superview is a stellar performer in all my scopes. I just tend toward the 18mm since it's parafocal.


Edited by PNW, 14 June 2020 - 12:57 AM.

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#19 FerrariMX5

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Posted 14 June 2020 - 01:56 AM

OK, good Tony,

 

Now we know why it worked well on Saturn and its rings.

An Ortho is a good planetary eyepiece.

My question to you is this, "Are you comfortable with using your 12.5mm Ortho ?"  "Would a 10mm Ortho be OK even if your eye needed to be slightly closer to the eyepiece ?" I have learned that I'm a barlowed Plossl guy, which is kind of how the zooms work. Make sense ?

 

Cheers,

 

Ed

Thank you, I am looking into a Barlow. 

A 1.5 Barlow might indeed fill the need and gaps for both the 32mm and perhaps the 12.5mm.

Also, looking at the used market for a Vixen 8-24mm zoom or a Televue 8-24mm "click-stop" zoom.

Might be best served by either of those suggestions.


Edited by FerrariMX5, 14 June 2020 - 02:02 AM.


#20 luxo II

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Posted 14 June 2020 - 09:54 AM

Many years ago with help from club members I did a trial involving about a dozen C8’s and their observers on several nights, on double stars and planets.

It showed for most observers with good vision there was a sweet spot around 8-9mm focal length for the eyepiece - below this the image was bigger, softer but no more detail was seen.

Hence I will suggest the Vixen zoom is an ideal match for your scope, or alternatively a 9mm ortho.

As above you also need to consider the effects of your surroundings on seeing - urban locations imply lots of thermal sources - houses, apartments and big buildings, car parks etc.

And on many nights the seeing is simply awful.

Edited by luxo II, 14 June 2020 - 09:56 AM.


#21 FerrariMX5

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Posted 14 June 2020 - 05:34 PM

I now own a 3x Barlow (Probably not much good for my situation) a 9mm and a 25mm.

 

Add that to my 12.5mm and 32mm and it looks like I have a fairly good spread.

 

Thank you to everyone for your comments.

We will see what lies in the future as we explore what has happened in the past.

 

Edit: Just used the 9mm on Saturn and again, it was an improvement, although staying on target was a bit of a challenge.

The 25mm was also a nice surprise and added to the experience.

The Barlow?   Not so much, but it was cheap.

A better quality, 1.5 Barlow, would round out my kit nicely.

 

Tony


Edited by FerrariMX5, 15 June 2020 - 02:22 AM.


#22 FerrariMX5

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Posted 14 June 2020 - 05:42 PM

Hi Tony & psyhiker,

 

Speaking of collimation, Tony AND/OR psyhiker, you may want to get a small mm eyepiece for "touching up your SCT's collimation" on the best of your viewing nights. This may be a 2.5mm, 3.0mm or 4mm eyepiece that lets you look so closely into a star that you can make out the airy disk and diffraction rings that your SCT produces on a "Point Source" aka Star. As you "pump up the magnification" you get well past the point where you optics can work and into the realm where the airy disk lives. But that's another discussion for another time . . .

 

Best Regards,

 

 

 

 

Ed, it is early in the game and I want to stay focused (Pun)

Collimation: not yet, everything seems to be working very well and I am too young into this to tackle collimation, like I would a carburetor on a lawnmower.

Once the stars hit the objective, I will challenge myself.

Thank you for all your help and look forward to the future when we can have that discussion.

Tony

 

EDIT:  Ed, trying out the 9mm on Jupiter, I took it out of focus and made the Planet quite large with a hole exactly in the center. I am assuming that since this was so well balanced on all sides and then focused fairly sharp when I brought it back into focus that collimation is probably not required at this time.  Next night out I will try this on a star and see how it looks, hoping I get the same results.  When the time comes I do want to try my hand at collimation. have to study up on what is required and how to test.   Thank you for your suggestion, it is now on my list of future adventures!


Edited by FerrariMX5, 15 June 2020 - 02:33 AM.


#23 eblanken

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Posted 15 June 2020 - 12:02 PM

Ed, it is early in the game and I want to stay focused (Pun)

Collimation: not yet, everything seems to be working very well and I am too young into this to tackle collimation, like I would a carburetor on a lawnmower.

Once the stars hit the objective, I will challenge myself.

Thank you for all your help and look forward to the future when we can have that discussion.

Tony

 

EDIT:  Ed, trying out the 9mm on Jupiter, I took it out of focus and made the Planet quite large with a hole exactly in the center. I am assuming that since this was so well balanced on all sides and then focused fairly sharp when I brought it back into focus that collimation is probably not required at this time.  Next night out I will try this on a star and see how it looks, hoping I get the same results.  When the time comes I do want to try my hand at collimation. have to study up on what is required and how to test.   Thank you for your suggestion, it is now on my list of future adventures!

Hi Tony,

 

Excellent approach taking the 9mm in-and-out of focus: You have shown that for you collimation is good !!! Star test would be good also, but what is convincing is your great results on Saturn with the 12.5mm Ortho.

 

You are on the right track. One additional experiment is to get the 12.5mm Ortho looking at Saturn and then swap in the 32mm with the barlow and see what you get: If the 3x barlow is good then that should work as well. The eyerelief and the focus is likely to be much different, so don't be thrown off. Try the 9mm, then back to the 32mm with the barlow and back to the 12.5mm Ortho. All these under the same conditions will tell you a lot about each one. I am delighted that your 12.5mm Ortho works so well in your SCT. That removes doubt about that entire combination. Whenever that 12.5mm combination isn't working, you can know that it is the sky and not your equipment on that night. Alternately, if the 12.5mm IS working and some other eyepiece combination doesn't give good results, blame it on the other combination.

 

Tell us more about the 9mm, another Ortho or a Plossl or something else ?

 

Ed (aka eblanken)


Edited by eblanken, 15 June 2020 - 12:07 PM.

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#24 Starman1

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Posted 15 June 2020 - 03:01 PM

I have:

a nexstar 8

a 12.5mm (1.25)

a 32mm (1.25 GSO Plossl).

a need for magnification beyond the 12.5mm

 

Used the telescope three times.

Once with the 12.5 (Found the moon), but could not find the stars.

Ordered the 32mm, found Saturn, Jupiter and quite a few stars, magnified the planets to 160 times, (using the 12.5mm).

Sharp, Great definition of rings..    160X is still small, did not see the moons circling either planet..

 

I am thinking I need an 8mm (But need advice before I order).

Was also thinking of a midrange 18mm (But, probably will always start with the 32mm then jump to 12.5, therefore this may very well be a waste).

 

Would I be better served with a 7mm?   

How about a 6mm?

 

Yes, it is all about Saturn right now, and perhaps a crater or two on the moon.

 

Just starting out, vintage N8, but it works like a charm.  (Circa 2002)

 

(Also, just got the star pointer and it really does work well)

 

 

Tony

Good set: 32mm, 20mm, 13-14mm, 10mm, 8mm

32mm for largest, brightest, field

20mm for highest acuity

13-14mm for optimum high power unbothered by seeing

10mm for a high power that might be bothered by seeing, but often usable

8mm for the highest practical magnification you'll probably use.

5mm is possible on those nights of "frozen" atmosphere with superb seeing--once or twice per decade.  Suggest making this one with a 2X barlow on the 10mm.


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#25 eblanken

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Posted 15 June 2020 - 03:47 PM

Good set: 32mm, 20mm, 13-14mm, 10mm, 8mm

32mm for largest, brightest, field

20mm for highest acuity

13-14mm for optimum high power unbothered by seeing

10mm for a high power that might be bothered by seeing, but often usable

8mm for the highest practical magnification you'll probably use.

5mm is possible on those nights of "frozen" atmosphere with superb seeing--once or twice per decade.  Suggest making this one with a 2X barlow on the 10mm.

Hi Don,

 

I like your recommendations for OP's 2000mm, 8 inch, f/10 SCT. 

 

He's probably fine with his 32mm and can possibly be satisfied with a 3x barlowed 32mm to get close to 10mm. (We will wait to hear back on that one case).

 

My only modification would be that OP seems happy with his 12.5mm Ortho for planets so I'd ask you your opinion: Does the 12.5mm Ortho adequately cover the slot for 13-14mm "unbothered by seeing" or would steer him in a different direction away from the Ortho to get more AFOV and TFOV ?

 

I (and probably others too) would like to know your thoughts.

 

Ed (aka eblanken)

 

 

He has a 9mm already, but I don't know about what type of eyepiece


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