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Large apertures easier for star hopping(?)

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#1 25585

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Posted 11 August 2020 - 06:43 PM

Using from 4" to 12", not exceeding 1600mm/ 60" FL, I find the larger apertures easier for manually star hopping and zoning in. Everything, is easier because its brighter. Provided TFOV remains the same, its like a more detailed ir zoomed-in map. And along the way more "discoveries" to investigate. Uranometria 2000 becomes my road atlas (shame no white on black field version printed).

 

So are GOTO mounts as much use for larger apertures up to certain FLs , or are DSCs better? Tracking seems the major advantage of GOTO, but would a platform fulfill that need as well?



#2 ButterFly

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Posted 11 August 2020 - 07:09 PM

Moving from NYC to a dark site, it was all just very confusing because there was more to sort through.  Even naked eye.  I got used to it.  If you are seeing deeper, a more detailed star chart is helpful.  Especially when looking for M31's globs or something of the sort.  If the true field of view is the same, the more stuff in that field is the only difference.  That can lead to confusion.  IDSA and supplement charts have worked well for me.

 

Tracking is a very nice feature.  Using a zoom eyepiece that's not exactly parfocal, like the Baader, is much friendlier with tracking.  I opted for ServoCAT over the platform for one reason.  It tracks satellites!  The ISS in a 15" is very nice and I won't get knocked off a ladder.  As more stations go up (and ehile being built) I feel I will be more and more satisfied with my choice.  Obviously, with many dobs, one platform can be used on all.  With either option, there is no need to use it if you don't want to for a particular session.  Just panning around aimlessly is lovely.


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#3 junomike

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Posted 12 August 2020 - 05:43 PM

Using from 4" to 12", not exceeding 1600mm/ 60" FL, I find the larger apertures easier for manually star hopping and zoning in. Everything, is easier because its brighter. Provided TFOV remains the same, its like a more detailed ir zoomed-in map. And along the way more "discoveries" to investigate. Uranometria 2000 becomes my road atlas (shame no white on black field version printed).

 

So are GOTO mounts as much use for larger apertures up to certain FLs , or are DSCs better? Tracking seems the major advantage of GOTO, but would a platform fulfill that need as well?

IME a larger OTA w/GOTO provides you with more options as you just start looking for faint fuzzies with any given aperture.

DSO's can work just as well but IME they haven't been as accurate as GOTO has.  YMMV
 



#4 stargazer193857

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Posted 12 August 2020 - 06:49 PM

Globular clusters in M31 are only 100x as far away as M13 is. So with some 12+ aperture and 300+ magnification, it does not sound far get fetched to spot a cotton ball or two.

True that field of view does not increase much below about 8-10", because of the small secondary or lack of eyepieces wide enough. So 12" is kind of a sweet spot, if not 10". Around 14" and especially 18" is when it narrows and gets challenging again.


Thanks for sharing that 12" is easy to star hop.

#5 Pinbout

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Posted 12 August 2020 - 08:58 PM

Using from 4" to 12", not exceeding 1600mm/ 60" FL, I find the larger apertures easier for manually star hopping and zoning in. Everything, is easier because its brighter. Provided TFOV remains the same, its like a more detailed ir zoomed-in map. And along the way more "discoveries" to investigate. Uranometria 2000 becomes my road atlas (shame no white on black field version printed).

 

So are GOTO mounts as much use for larger apertures up to certain FLs , or are DSCs better? Tracking seems the major advantage of GOTO, but would a platform fulfill that need as well?

shooting a green laser thru a wide angle eyepiece is the easiest way to star hop, whatever it points to is in the eyepiece


Edited by Pinbout, 12 August 2020 - 08:59 PM.


#6 KBHornblower

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Posted 12 August 2020 - 09:22 PM

In my experience a 50mm finder helps in star-hopping.  Last fall I was able to star-hop to Uranus and Neptune from my back yard, under severe light pollution.  With good transparency I could see 8th magnitude stars and Neptune in the finder, and thus follow a chart.

 

Edit:  That's an RACI finder, after starting at a naked eye star with the Telrad.


Edited by KBHornblower, 12 August 2020 - 09:26 PM.

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#7 Bill Weir

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Posted 12 August 2020 - 10:59 PM

shooting a green laser thru a wide angle eyepiece is the easiest way to star hop, whatever it points to is in the eyepiece

I used to do that for an imaging friend so he didn’t have to find things with the refractor that had the camera attached. He didn’t have GoTo. I’d find the object then shoot the laser and he’d line up on it with his red dot. Then he’s snap a few quick frames to get the framing right. It worked very well.

 

With my 6” and 20” all I have is a Telrad. A wide field eyepiece is all I need after starting on a bright star. A 20mm 100° eyepiece gives about a degree with my 20”. The grids in Uranometria are 1° so what more do I need? I can star hop to an object pretty quick. A finder scope is just one more thing to set up. The 20” has Sky Commander and Skytracker but I have it for the tracking. On most nights I don’t set up the electronics.

 

Bill


Edited by Bill Weir, 12 August 2020 - 11:00 PM.


#8 Jon Isaacs

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Posted 13 August 2020 - 03:20 AM

Using from 4" to 12", not exceeding 1600mm/ 60" FL, I find the larger apertures easier for manually star hopping and zoning in. Everything, is easier because its brighter. Provided TFOV remains the same, its like a more detailed ir zoomed-in map. And along the way more "discoveries" to investigate. Uranometria 2000 becomes my road atlas (shame no white on black field version printed).

 

 

In my experience, I find that the larger the scope, the more difficult it is to star hop.

 

- The TFoV is not constant, it's inversely proportional to the aperture, more or less, smaller scopes with shorter focal lengths have wider fields of view.  A 4 inch F7 can be a super finder with a 3.7° field.

 

-Larger scopes go deeper, objects are smaller, fainter, and there's more of them. Hunting down 13th magnitide galaxies in a 12 inch means not only finding it but carefully distinguishing it from the other 13th magnitide galaxies. In a 4 inch, they aren't so many, if you see it, that is likely it.

 

-  There's a good chance if looking for an object in a smaller scope, I've seen it before in a larger scope so I'm familiar with it.

 

- With larger scopes, I mostly star hop with the finders and rather tha the main telescope. 

 

That's how it works for me. My 12.5 is relatively easy to star hop with, particularly when compared to the 16 inch and the 22 inch.. But the NP-101 is the easiest, it's capable of 4.9° at 13x, 3.8° at 26x, about 1.5° at 67x, but it's super finder all by itself.

 

Jon

 


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#9 Illinois

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Posted 13 August 2020 - 06:27 AM

I never use star hopping and I know the sky very well. I use star maps and red dot finder.  Point to general area that is where I think it is and I use low power eyepiece to find it! 


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#10 bobhen

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Posted 13 August 2020 - 06:47 AM

Using from 4" to 12", not exceeding 1600mm/ 60" FL, I find the larger apertures easier for manually star hopping and zoning in. Everything, is easier because its brighter. 

I “kind of” know where you are coming from…

 

Since I started using my image intensifier, which of course adds a significant light gathering boost to a same-size telescope when compared to just observing with regular glass, I have found it easier and more productive to use the main scope to do more extensive and wider panning around.

 

I might use a red dot finder to get a general location and I might use an optical finder to locate star patterns but the main scope with the added light gathering of the intensifier is now more conducive and also “more productive” to use to pan around a larger/wider area because objects now stand out more and are more easily observed when compared to non-intensified observing. I would presume that a larger mirror would have a similar effect.

 

I've noticed this even with my C8, with its 2,000mm FL.

 

Bob



#11 Jon Isaacs

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Posted 13 August 2020 - 08:50 AM

I might use a red dot finder to get a general location and I might use an optical finder to locate star patterns but the main scope with the added light gathering of the intensifier is now more conducive and also “more productive” to use to pan around a larger/wider area because objects now stand out more and are more easily observed when compared to non-intensified observing. I would presume that a larger mirror would have a similar effect.

 

 

Panning to find an object is often referred to as "star hoping" rather than "star hopping." 

 

Star hopping, at least in my mind, is a collection of techniques one uses to precisely locate and identify an object or group of objects.

 

The short focal of a smaller scope is what makes star hopping easier, at least in my experience. 

 

Without the intensifier, large aperture scopes still require smaller exit pupils just to see the object, that means even narrower fields of view and more precise star hopping. 

 

Jon



#12 tommm

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Posted 13 August 2020 - 11:02 AM

...Tracking seems the major advantage of GOTO, but would a platform fulfill that need as well?

Yes, they both will provide tracking, but GOTO is built into the scope so it is one less thing to transport and set up.  A large dob, say 20" or larger you will likely need a ramp to roll the scope onto the platform, so more to transport. 

 

I've used both, and I like GOTO better for the above reasons. It's integrated into the scope so it's just there automatically. I can also generally find things more quickly than I could star hopping. I generally use a WO16mm 82 deg eyepiece on a 2358 mm f.l. scope (includes P2) which gives 0.56 deg true fov and a bit less than 150x to do initial scope alignment and find objects. An object is usually in that fov or very close to it (near the edge of the inner circle in the Rigel finder) after a GOTO, and adjusting the scope to put the target inside the circle puts it in the main scope field of view.

 

I think a platform would be more convenient for a scope of smaller size, say 16" or less, since you can lift the scope and set it on the platform, no need for a ramp.  The platform also doesn't need to be as large and heavy as it does for a 20" or larger scope. For me its a lot about convenience, because I will use it more if the barrier to use is not as high.

 

I think DSC's work about as well as GOTO, depending on the product (as does GOTO), but as you say, no tracking. I really like tracking because I don't have to worry about loosing the object once it is targeted.  I can converse with someone, read about the object in Sky Safari, get distracted doing other things, and go back to the eyepiece and it is still there.

 

But opinions are all over on this, with some preferring star hopping and no DSC or tracking, some DSC only, some GOTO...You will of course have to consider the various opinions, weigh the factors and decide which suits you.


Edited by tommm, 13 August 2020 - 11:02 AM.



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