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Terrestrial and a 8' Edge...

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#1 HarryBnBad

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Posted 18 August 2019 - 09:46 PM

Ok. I'm bored to hell. It been raining just way to long. ( tampa )

So what's needed for daytime.

Looks like I need a erect image Prism.

I've got a great 2inch diagonal. So I'd like to keep it at 2inch. I like my 2inch eyepieces.

But for daytime, is there anything I should looking in a Prism?

Most important. Right side Up.

#2 Spikey131

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Posted 19 August 2019 - 11:54 AM

You don’t need a prism. In a mirror diagonal the view will be reversed but right side up. You do need long focal length EPs. Even a 55mm gives you 36x, which is what you want to start with terrestrial viewing.

#3 baondayko

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Posted 19 August 2019 - 12:03 PM

I think an 8 foot scope is way beyond what is necessary for daytime viewing. :)


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#4 HarryBnBad

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Posted 19 August 2019 - 04:40 PM

I wish I had a 8 foot scope
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#5 HarryBnBad

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Posted 19 August 2019 - 04:43 PM

Its 8inch edgehd sct.

And yes it's not the best for daytime, or even nighttime terrestrial viewing. But I tr s all I have. So I thought I'd make the most of it.

Who knows, maybe I'll have a camera attached when I see a UFO during daytime.

#6 Rovert9988

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Posted 19 August 2019 - 06:41 PM

I've used my 8" Edge for terrestrial viewing before. I watched a hawk build a nest one afternoon from the comfort of my backyard despite the bird being quite a ways off.

The biggest issue was thermals. If I kept everything in shade it was okay, but if the sun hit my scope I got fairly bad thermal currents. I would take a decent refractor for terrestrial viewing given the choice, but the Edge can work.
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#7 Castor

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Posted 19 August 2019 - 06:42 PM

Hi HarryBnBad,

 

I believe an 8-inch SCT is not the best scope for doing casual terrestrial viewing during the day, but with the proper eyepiece and prism diagonal it can do very well for long distance viewing in low-light conditions (at twilight or at night) or during the day if the air is stable without heatwaves causing shimmering as it happens sometimes on overcast days.

 

For terrestrial viewing I’d recommend getting a nice (not necessarily super expensive) ED spotting scope or a small (70mm – 80mm) doublet refractor with ED glass -for good correction of chromatic aberration (CA), actually more bothersome for terrestrial use than for wide field deep-sky viewing.

 

But since you acknowledge that you are aware that an 8-inch SCT scope is not ideal for daytime terrestrial viewing and still insist on using yours for that purpose, the least I can do is mention a couple of correct image prism diagonals that could work for your scope, assuming that you already have a 2-inch visual back installed on your scope compatible with smooth barrel refractor-type diagonals –you mention having “a great 2inch diagonal” or that you are ok with attaching a prism diagonal to the threaded back of your scope.

 

The normal diagonal for terrestrial viewing is one with 45-degree angle (same used with angled spotting scopes).  For the particular type of terrestrial viewing that I do with my Meade 8-inch LX200 f/10 SCT OTA I use a Tele Vue 1.25” 45-Degree Erecting Prism Diagonal (AMI-0011), but unfortunately it has been discontinued, see here:

https://www.bhphotovideo.com/c/product/329505-REG/Tele_Vue_AMI_0011_45_Degree_Erect_Image_Diagonal.html

 

Here are a few pictures of the setup that I use with my 8-inch SCT:

https://www.cloudynights.com/topic/672974-your-experience-using-6-inch-8-inch-schmidt-cassegrain-telescopes-scts-as-spotting-scopes-for-terrestrial-observingviewing-in-low-light-conditions/?p=9579329

 

There is a plethora of 1.25” 45-degree erecting prism diagonals available on the market that you could use with your scope with minimal expense if you have a 1.25” visual back (usually included with the scope) or a 2” to 1.25” adapter (the one that came with your 2” diagonal) to use the 1.25” prism in your 2” visual back.  Most of them create some vignetting with lowest-power wide-angle 1.25” eyepieces like a 24mm 68-degree eyepiece but they do fine with eyepieces that have a smaller field stop like a 26mm Plossl.

 

In your OP you state that like your 2 inch eyepieces and that you want to keep the diagonal at 2-inch too.  That would limit your choices and bring the cost up, but if you are determined to get a 2-inch prism these are the two 2-inch 45-degree Erecting Prism Diagonals that I know of:

 

The first one (Astromania) would work on a 2-inch focuser or visual back (I suppose that’s what you have on your SCT):

https://www.amazon.com/Astromania-45-Degree-Erecting-Diagonal-Telescope/dp/B01B2OR23U/ref=sr_1_2?keywords=2-inch+erecting+prism&qid=1566255542&s=gateway&sr=8-2

 

The second option (Baader) is designed to be threaded directly to the back of most Celestron and Meade SCTs:

https://agenaastro.com/baader-2-45-amici-prism-sct-diagonal-2956151.html

 

I haven’t tried those diagonals and I have never owned an Edge scope so I can’t comment on compatibility or suitability, but I have been considering buying the Astromania 2-inch 45-Degree Erecting Prism Diagonal for my scopes.  Using 2-inch eyepieces for terrestrial viewing is a luxury to me, so I am not yet convinced about spending $189 on one, but I might do that in the future.

 

I hope that it helps!


Edited by Castor, 19 August 2019 - 08:30 PM.


#8 Dwight J

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Posted 19 August 2019 - 06:47 PM

Low magnification will show the shadow of the secondary.  50 to 60 X may be a good place to start.  Two star diagonals will act as a porro prism.  Near focus may be a ways away, maybe 30 to 50 feet.  I am sure someone will post more exact figures as these are just dim recollections.  



#9 HarryBnBad

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Posted 20 August 2019 - 11:46 AM

Looks like I might try the William optics 2" erect imaging diagonal.

Oh, as for my setup. I have the 2inch click lock.

I feel a few people are taking this like I'm dead set on doing terrestrial viewing.

Not at all. It's just in tampa florida I've only had 1 night in 3 months with clear skies. And that only lasted 2.5 hrs.

Thought I'd learn a new art, and keep my scope skills sharp.

Thanks again for all the info...

#10 HarryBnBad

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Posted 20 August 2019 - 11:46 AM

Looks like I might try the William optics 2" erect imaging diagonal.

Oh, as for my setup. I have the 2inch click lock.

I feel a few people are taking this like I'm dead set on doing terrestrial viewing.

Not at all. It's just in tampa florida I've only had 1 night in 3 months with clear skies. And that only lasted 2.5 hrs.

Thought I'd learn a new art, and keep my scope skills sharp.

Thanks again for all the info...


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