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Jeff2011
Carpal Tunnel
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Reged: 01/01/13

Loc: Sugar Land, TX
Re: to view peleades? new [Re: Jon Isaacs]
      #5605739 - 01/04/13 11:06 PM

Jon,

Your explanation on true fov calculation using the f stop of the eyepiece is very interesting. How would this work for the baader Hyperion eyepieces. They have a built in Barlow type element that is 1.25 but the rest of the eye piece is like a 2 inch. I happened to pick up a used 13 mm Hyperion for 60 bucks. It gives me about a 3/4 deg TFov. The afov is 68.

Thanks,

Jeff


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Widespread
professor emeritus


Reged: 05/11/11

Loc: Bowling Green, Kentucky
Re: to view peleades? new [Re: Jeff2011]
      #5606015 - 01/05/13 04:39 AM

Last night I tried my new 36 mm Baader Planetarium (72 degree field of view) in my St80.

Jupiter was a tiny dot, with lots of false color (due to the scope, not the eyepiece), but the Pleiades and Hyades were outstanding. This is my lowest magnification telescope view ever.

The Seven sisters blew me away. The view was lower magnification than my 15x binoculars, but rock solid. I have my binoculars on a mono pod, but not a tripod, so it's always a little bit shaky.

This is a modular eyepiece, and can be used with either 1.25 or 2 inch diagonals. It gives the widest TFOV possible in 1.25" format.

In a 2" diagonal, the view is even wider, of course. Used with a 6.3 focal reducer, it should give the maximum (vignetted) TFOV for an 8SE.

It's still won't quite fit the Pleiades, though.

Cheers, David


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: to view peleades? new [Re: Jeff2011]
      #5606224 - 01/05/13 09:59 AM

Quote:

Jon,

Your explanation on true fov calculation using the f stop of the eyepiece is very interesting. How would this work for the baader Hyperion eyepieces. They have a built in Barlow type element that is 1.25 but the rest of the eye piece is like a 2 inch. I happened to pick up a used 13 mm Hyperion for 60 bucks. It gives me about a 3/4 deg TFov. The afov is 68.

Thanks,

Jeff




Jeff

With eyepieces like your Hyperion one uses an effective field stop diameter. Televue provides this for information all their eyes as do some other vendors. One can also measure the Tfov by measuring the time a particular star takes to drift across the field and then back calculating the field stop.

One can search the web and find values that may or may not be correct.

I always use the field stop to calculate the Tfov because it is more accurate but for most practical purposes tfov = AFoV/mag is plenty good, generally within 5% though sometimes it might be as much as 10%. In my experience, it always overestimates the Tfov.

Jon


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Jeff2011
Carpal Tunnel
*****

Reged: 01/01/13

Loc: Sugar Land, TX
Re: to view peleades? new [Re: Jon Isaacs]
      #5606465 - 01/05/13 12:07 PM

Jon,

As I was reading your reply I had a slap my head moment. Baader does publish the F stop information in a nice little PDF at http://www.baader-planetarium.com/pdf/hyperion_brief_description_e.pdf

Thanks for taking the time to respond to us newbies. I have learned a lot in a year and a half by reading posts such as yours and am trying to pay it back by helping others.

Thanks,

Jeff


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Jeff2011]
      #5607269 - 01/05/13 08:40 PM

"The Seven sisters blew me away."
"It's still won't quite fit the Pleiades, though."

You mean you can see the seven sisters only in the EP, and not the two parents?
The Pleiades are the seven sisters and two parents.


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Pat at home
sage


Reged: 03/16/07

Loc: Campbellton, New Brunswick, Ca...
Re: to view peleades? new [Re: brianc99]
      #5607337 - 01/05/13 09:33 PM

Quote:


Pleiades are my absolute favorite feature of the night sky. Granted, my viewing experience is very limited. But most of what I view makes me think "that's interesting" or "that's cool," while the Pleiades make me think "that's one of the most beautiful sights anyone has ever seen."

Brian




I once made the mistake of "looking up" with a pair of binoculars and the first thing I saw were the Sisters.

The next day my wallet was empty but I had an 8 inch newtonian on an EQ6-Pro in my yard. I've not regretted that one bit. The Sisters are still a favourite winter target for me. I always make a point of aiming my ST-80 that way whenever someone new comes over to the house and are curious about astronomy.


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Pat at home]
      #5607382 - 01/05/13 10:08 PM

I can fit the Pleiades in my Meade 4000 series "26mm" EP. They only have a 52 degree aFOV. It's a little stuffed, but it can be done. Some site's say Pleiades is 110' but I look at it as the seven sisters and two parents. And that don't take 110' to do that. Stellarium says it's only 30' but I don't think that includes the 2 parents.

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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: to view peleades? new [Re: Dennis_S253]
      #5607523 - 01/05/13 11:27 PM

Quote:

I can fit the Pleiades in my Meade 4000 series "26mm" EP. They only have a 52 degree aFOV. It's a little stuffed, but it can be done. Some site's say Pleiades is 110' but I look at it as the seven sisters and two parents. And that don't take 110' to do that. Stellarium says it's only 30' but I don't think that includes the 2 parents.




The 7 sisters are about a degree but the entire cluster is about 2 degrees.
Personally I like to see the whole thing plus a little to frame them.

Jon


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Jon Isaacs]
      #5607573 - 01/05/13 11:53 PM Attachment (15 downloads)

Well, here's your 2 degree framed.

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Dennis_S253]
      #5607577 - 01/05/13 11:55 PM Attachment (12 downloads)

And here's my stuffed view

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Dennis_S253]
      #5607578 - 01/05/13 11:56 PM

I like mine better

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Dennis_S253]
      #5607586 - 01/06/13 12:02 AM Attachment (10 downloads)

Maybe I shouldn't have inverted the colors. Lets try again..
2 degree...


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Dennis_S253]
      #5607589 - 01/06/13 12:03 AM Attachment (10 downloads)

Stuffed...

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Dennis_S253]
      #5607599 - 01/06/13 12:11 AM

I had to fudge the numbers on the 40mm to get the 2 degree FOV but theres your framed view. I still like mine better. So is this a personal preference? I just wanted to know what they were looking at. Show me some pics... Maybe there looking at the Hyades???

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: to view peleades? new [Re: Dennis_S253]
      #5607839 - 01/06/13 07:36 AM

Dennis:

I am looking at your scope list and I believe the widest field of view is possible is with your 6 inch with the 1000mm focal length which has a 1.25 inch focuser. My calculation based on the field stop indicates the maximum possible field of view is no more than 1.6 degrees, enough to take in most of the cluster.

At some level it is a matter of personal choice but it is worth remembering that a scope capable of framing the Pleiades in a 2.5 degree TFoV is also capable of a 1.6 degree view or whatever else might be of interest. So, if one is looking for a scope well suited for viewing the Pleiades, one that can show all the different aspects is nice to have.

Jon Isaacs


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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: to view peleades? new [Re: Dennis_S253]
      #5607957 - 01/06/13 09:33 AM

That's missing my very favorite feature, chopping off the chain reaching down to HIP 17776.

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Perigny270
super member


Reged: 10/23/11

Loc: Temiscaming, Quebec
Re: to view peleades? new [Re: Tony Flanders]
      #5608141 - 01/06/13 11:33 AM

I look for them every time I go out. Any time, for any reason. If I want a real lift, I reach for the binos. Top of the list for first time viewers. But my favourite is 31mm Baader aspheric in my 102 APO. It was the first thing I looked at with that EP - I couldn't tear myself away from it. These days it's a double treat as it's a short jaunt to Jupiter and Aldebaran...

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: to view peleades? new [Re: Tony Flanders]
      #5608143 - 01/06/13 11:33 AM Attachment (5 downloads)

Yes Jon, I know the limitations of my scope very well. That's why I said I had to "fudge" the numbers to get the 2 degree FOV. If you want to "frame" the Pleiades in a 2 degree FOV then that's a personal preference. But it is not required to see the seven sisters and 2 parents. I was wondering if someone was confusing Pleiades and Hyades. That was why I questioned it.
LOL Tony, that's one of my favorites also. That's why I use my 32mmm.


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newtoskies
Pooh-Bah


Reged: 07/15/12

Loc: SE Ma.
Re: to view peleades? new [Re: Dennis_S253]
      #5608156 - 01/06/13 11:41 AM

Yep, my favorite as well and view it every time when the scope is out, or the binos. I use my 32mm and get good views.

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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: to view peleades? new [Re: Dennis_S253]
      #5608467 - 01/06/13 02:05 PM

Quote:


Yes Jon, I know the limitations of my scope very well. That's why I said I had to "fudge" the numbers to get the 2 degree FOV. If you want to "frame" the Pleiades in a 2 degree FOV then that's a personal preference. But it is not required to see the seven sisters and 2 parents. I was wondering if someone was confusing Pleiades and Hyades. That was why I questioned it. LOL Tony, that's one of my favorites also. That's why I use my 32mmm.




Dennis:

M-45 consists of more than just the 7 sisters and two other bright stars. Most sources seem to identify M45 as being 2 degrees. It's worth nothing that M45 is different than many clusters because one sees about all there is to see with a relatively small scope. In contrast, M-7 is quite different in this regard. It is very nice in a smaller scope but if one points a 16 inch scope at M7, one suddenly sees a great deal more.

So, to play the devil's advocate, your 32mm eyepiece provides something close to a 1.6 degree field of view, if you scope were capable of a 2.0 or 2.5 degree field of view, would the 1.6 degree TFoV still be your preference?

Jon


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