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Should I Get Rid of the Telrad?

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#76 ckwastro

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Posted 29 January 2013 - 02:06 PM

As far as how the Telrad was "meant to be used", I can say that one can use a Telrad to do far more accurate pointing than just finding the first guide star or pointing to an asterism...........Myself, the Telrad is the first line...


+1 :waytogo:

I concur, if it's not going to be used in this way, and it just doesn't work for Mike's needs, then by all means he needs to dump it.

#77 Sarkikos

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Posted 29 January 2013 - 02:34 PM

Jon,

As far as how the Telrad was "meant to be used", I can say that one can use a Telrad to do far more accurate pointing than just finding the first guide star or pointing to an asterism.


But often not as accurate as a good optical finder. ;) Certainly, a Telrad is all that's needed for many of the Messier objects, large and bright star clusters, brighter double stars and the like. But for small faint DSO, especially ones in a rich star field, an optical finder or "finder eyepiece" is a much more accurate tool. How could they not be more accurate than the naked eye? For such objects the Telrad is only the beginning.

In general, when I use the Telrad, the "first guide star" I point it to is the last naked eye star that is close to the location of the intended object. Otherwise, I might use geometrical triangulation. In either case, I then go to the optical finder. This makes the most sense. Why star hop when there are no more stars to see?

Myself, the Telrad is the first line, if I can't find it with the Telrad, then comes the magnifying finder...



Up to now, at least, the Telrad has been the first line, also, and sometimes is all that is required. But lately since I've been looking for mostly small or dim objects toward the LM of my telescope, the Telrad alone is not enough. I'm sure there are many "easy" objects that I could locate with the Telrad alone, but I'd get tired of looking at them over and over.

Mike

#78 David Knisely

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Posted 29 January 2013 - 02:39 PM

Sarkikos posted:

I don't see a Telrad alone leading anyone to a dim stellar planetary, a faint galaxy in a galaxy cluster or a tiny loosely-scattered OC in the midst of a Milky Way star field. There are many objects up there that need the additional help of a printed star chart, Sky Safari, optical finder and/or a finder eyepiece to locate.


Well Mike, for ID-ing a single galaxy in a galaxy cluster, the Telrad alone might or might not be enough. In any case, the Telrad will definitely get the scope more than close enough to the target to allow it to be well within the field of a low to moderate power eyepiece. I remember the first time I saw a Telrad used properly on a "serious" telescope when one of our club members had one of the first 20 inch f/5 Obsession Dobs at our observing site (ZLM 6.0 to 6.6 typically). I was kind of shocked to see that the only finder he had on that monster was a Telrad! I had some serious doubts about the Telrad and what he could find with it, but in point of fact, he was running rings around me with my scope on its German equatorial mount and its 8x50 straight-through finderscope. He was finding faint galaxies and galaxy clusters with ease. He even shamed me a little by quickly showing me the stellar dot of the quasar 3C-273, again only using his Telrad on the big scope. I then started paying a little more attention to what he was doing. I noted his little 3-ringed clear plastic home-made Telrad overlays that he used with his atlases and then started to understand exactly how he was finding things by matching the patterns of the faint stars in and around the reticle of the Telrad itself to his atlas overlays as they sat on his charts. I soon purchased a Telrad of my own and began to fully understand that this is no "red-dot" finder, but a very useful tool which can make things easier for some people. Indeed, I often rely on the Telrad alone for finding the Perseus Galaxy Cluster (Abell 426), Abell 262 in southeastern Andromeda, the Coma Berenices Galaxy Cluster (Abell 1656), and the Hercules Galaxy Cluster (Abell 2151). Indeed, there are a number of nearly stellar planetaries that I can get near the center of the field of view using only the Telrad (Campbell's Hydrogen Star for one example).

Nobody said the Telrad can "do it all", but in the hands of one who understands how to properly use it, it can definitely be a very very useful tool. Clear skies to you.

#79 Sarkikos

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Posted 29 January 2013 - 02:49 PM

David,

Well Mike, for ID-ing a single galaxy in a galaxy cluster, the Telrad alone might or might not be enough. However, the same could be said for some optical finders.


Yes, this is true. But for me the important point is to position the location of the object in the main telescope's eyepiece. To do that, I don't need to see the object itself in the Telrad or the optical finder. The optical finder, however, will show me the location more accurately and allow me to position that location more precisely in the eyepiece.

In any case, the Telrad will definitely get the scope more than close enough to the target to allow it to be well within the field of a low to moderate power eyepiece.


This is true, also. But if use my 15x70 optical finder in tandem with Sky Safari, I can easily get close enough to the target that I can see it toward the center of field of a moderately high power eyepiece. Often I don't even need a "finder eyepiece."

Mike

#80 Starman1

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Posted 29 January 2013 - 03:00 PM

David,

Well Mike, for ID-ing a single galaxy in a galaxy cluster, the Telrad alone might or might not be enough. However, the same could be said for some optical finders.


Yes, this is true. But for me the important point is to position the location of the object in the main telescope's eyepiece. To do that, I don't need to see the object itself in the Telrad or the optical finder. The optical finder, however, will show me the location more accurately and allow me to position that location more precisely in the eyepiece.

Mike


You aren't looking for faint targets, then. Most of the objects I've been viewing recently aren't visible in a 50mm finder either, because they're too faint or too small. I'd need a 100mm finder just to begin to see the faint spots and even then that might not be enough.

It's the reason I don't rely on finders at all but use my Sky Commander to find nearly everything. I don't use it for the really bright stuff--familiarity with locations make using the Telrad sufficient. But for the various NGC, UGC, MCG, ESO, and PGC objects, the Sky Commander beats any finder.
And then the eyepiece becomes the optical finder once you're there.

My main use for the Telrad is to find the bright stuff, and to pinpoint the object I'm looking at for the guy with the neighboring scope to use his Telrad to find it. :grin:

I grant you, though, that a lot of objects ARE visible, and centerable, in a 50mm finder.

#81 Jon Isaacs

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Posted 29 January 2013 - 03:03 PM

But often not as accurate as a good optical finder. Certainly, a Telrad is all that's needed for many of the Messier objects, large and bright star clusters, brighter double stars and the like. But for small faint DSO, especially ones in a rich star field, an optical finder or "finder eyepiece" is a much more accurate tool.



See David's post below. I am not as skilled as the person David is mentioning but I am finding far more than Messier objects, bright clusters, bright double stars. For example I can place the group of galaxies that includes NGC5444 in the field of view of my 16 inch or even the 25 inch. Last year I was quite tired and was having the devil of a time finding Hickson 68, a favorite group. Instead I found the 9th magnitude Globular 5466... I had reversed Arcturus and Alkaid.

Jon

#82 csrlice12

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Posted 29 January 2013 - 03:38 PM

I actually use both the Telrad and the RACI. I'll find the object with the Telrad, then check in the RACI to see if what I'm looking for is in the FOV of the finder (usually is). It's also usually in the scopes FOV too; just like to check before looking thru the eyepiece.

#83 David Knisely

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Posted 29 January 2013 - 03:50 PM

I hate the Telrad! I have turned down the purchase of used scopes because it was mounted to them. In my mind it devalues them. I think for dobs they may be the right choice, but when I see these slapped on top other scope types...I cringe!!! :tonofbricks: Just me and my own hang-up!

:bow:I'm of the same belief. They add nothing to a scope's looks especially classics. Only possible exception would be a dob. :help: Mike


Who cares what the scope looks like? It is what you look *at* with the scope that is important, and for that, the Telrad can make the finding experience a lot easier. If I see the Telrad on either a multi-thousand dollar high end refractor or a little home-brew Dob, I know the user of each scope truly understands the value of that simple little reticle finder. Clear skies to you.

#84 rmollise

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Posted 29 January 2013 - 05:14 PM

If mine gave out a Rebel Yell, I'd definitely get rid of it!


More's the pity! :lol:

#85 Sarkikos

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Posted 29 January 2013 - 07:46 PM

Come on now, all that was settled many moons ago. :ubetcha: But it seems we're still feuding over Telrads.

:grin:
Mike

#86 Sarkikos

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Posted 29 January 2013 - 08:05 PM

Don,

David,

Well Mike, for ID-ing a single galaxy in a galaxy cluster, the Telrad alone might or might not be enough. However, the same could be said for some optical finders.


Yes, this is true. But for me the important point is to position the location of the object in the main telescope's eyepiece. To do that, I don't need to see the object itself in the Telrad or the optical finder. The optical finder, however, will show me the location more accurately and allow me to position that location more precisely in the eyepiece.

Mike


You aren't looking for faint targets, then. Most of the objects I've been viewing recently aren't visible in a 50mm finder either, because they're too faint or too small. I'd need a 100mm finder just to begin to see the faint spots and even then that might not be enough.


:thinking: I don't get the point. Or maybe you didn't get my point. I try to make myself clear, but I don't always succeed. :shrug:

I was just saying that, yes, I don't see most of the objects I'm looking for in the optical finder. But I do see their location.

In other words, I can see the specific grouping of stars that surround the object. That's all I need. It's not necessary to actually see the object itself in the finder. I center the location of the object - as shown by SkySafari on my Android tablet - behind the crosshairs of the optical finder. No, usually I don't see the object in the finder. That is precisely because it is a faint target I'm looking for. But I will see it in the eyepiece of my main scope.

And for me, I like to have that extra magnification and ability to see fainter stars that the optical finder gives me beyond the naked-eye view of the Telrad. These advantages help me to get a better fix on the location of the faint object, even if I can't actually see it until I look in the main telescope.

When I'm looking in the optical finder, the most important thing is getting the location centered precisely, whether or not I can actually see the intended object. For many faint objects, centering that location is much easier to do with a finder that magnifies and brightens the environs of the object.

Remember, I don't usually have a "finder eyepiece" in the focuser of the telescope. I think many people - I'm not saying all - rely on a "finder eyepiece" to find the object after star hopping with the Telrad. Then they may switch to a shorter focal length for a higher power view. I go from a quick look through the Telrad, to a star hop with the optical finder to center the location of the object, then straight to a medium to higher power eyepiece in the telescope - depending on the object.

So, AFAIK, many observers are actually using that "finder eyepiece" in lieu of an optical finder after positioning the scope with the Telrad. I'd rather do most of my star hopping with the optical finder.

To each their own. Whatever works.

Mike

#87 Starman1

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Posted 29 January 2013 - 08:42 PM

Well, we're agreed. if your star charts go a few magnitudes deeper than naked eye, an optical finder is the way to identify the field location.
Bear in mind that a lot of dob owners use BOTH types of finders on their scopes.
And for what it's worth, a lot of DSOs are visible in a 50mm finder.
Sometimes I've been surprised at how many.

#88 Jaimo!

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Posted 29 January 2013 - 09:00 PM

Well, we're agreed. if your star charts go a few magnitudes deeper than naked eye, an optical finder is the way to identify the field location.
Bear in mind that a lot of dob owners use BOTH types of finders on their scopes.
And for what it's worth, a lot of DSOs are visible in a 50mm finder.
Sometimes I've been surprised at how many.


I use both...

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Jaimo!

#89 Sarkikos

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Posted 29 January 2013 - 10:36 PM

Don,

Well, we're agreed. if your star charts go a few magnitudes deeper than naked eye, an optical finder is the way to identify the field location.


Yes indeed. As I'm star hopping with the optical finder, I'm comparing the view in the finder with the star positions in SkySafari on my tablet. The tablet is light enough that I can hold it in one hand as I look through the finder. But the tablet is 10.5" wide, large enough to give me a nice easy vista for star hopping in context.

I prefer this method to any involved use of Telrad degree circles, preplanning star hops based on those circles, and making a series of extended hops with the Telrad. My method takes not much more planning than generating an Object List in SkySafari. That's about it. No need to draw a series of Telrad circles on charts and preplan star hops. I do all of that on-the-fly by the telescope at the dark site.

Bear in mind that a lot of dob owners use BOTH types of finders on their scopes.


I think maybe most of us use both types of finders. So do I. I'm just considering replacing the Telrad with the ES finder, which would give me a straight-through erect-image view like the Telrad, but with more magnification and the ability to display dimmer stars. That is something I've wanted ever since I first started using a Telrad.

And for what it's worth, a lot of DSOs are visible in a 50mm finder.
Sometimes I've been surprised at how many.


That's true. And even more are visible in a 70mm! I was lucky to find a little bargain basement 70mm achromat with a surprisingly good objective, that I could upgrade to become a very nice finder and RFT.

:grin:
Mike

#90 Joe Bergeron

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Posted 30 January 2013 - 04:14 AM

If I'm not mistaken, the length of the Telrad permits a greater distance between the reticle and the viewing window, which reduces parallax. With the small Rigel Quickfinder, if you move your head behind it you will see the reticle shift relative to the star field. You don't see as much of that with a Telrad.

#91 RogerRZ

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Posted 30 January 2013 - 05:05 AM

If I'm not mistaken, the length of the Telrad permits a greater distance between the reticle and the viewing window, which reduces parallax. With the small Rigel Quickfinder, if you move your head behind it you will see the reticle shift relative to the star field. You don't see as much of that with a Telrad.


Mine is mounted at the front of my MN65, which is in turn mounted high enough to need a step stool to reach the eyepiece.

I always view through the Telrad from the back of the OTA, roughly three feet away. That's very decent eye relief. :-)

#92 JMW

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Posted 30 January 2013 - 06:02 AM

Yes, it's your scope, do what you want.

I use Sky Commander or Argo Navis on my push to mounts. I often have a TEC-140 on a Discmount DM-6 and a large dob set up for viewing. I have a Telrad on a bracket on the top of my Discmount so I don't have to put it on the tube of my TEC-140. I have another Telrad on the OTA of the Obsession 20F5. I can't imaging using a large truss dob without a Telrad.

Here are my reasons to use the Telrad.

Not sensitive to eye placement, can be used with eye several feet behind Telrad.
Get's you to the star neighborhood before getting on the tall ladder.
Quickest way to show the public or other astronomers where your scope is pointed at.
After finding object with first scope, just move second scope to match up Telrads.
Fasted way to know your scope is pointed to the correct alignment star when setting up DSC.
Batteries last forever, don't event worry about remembering to turn it off.
Lots of sky charts and astronomy apps support using the tetrad circles.
When used with a great wide field eyepiece, you may not need a 2nd optical finder.
Large lever makes it easy to adjust brightness to match observing situation.
It's inexpensive and just works.

#93 Sarkikos

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Posted 30 January 2013 - 08:24 AM

I think for now I might attach the ES finder to my C6 to get a feel of how it performs in the field before I start drilling holes in my 10" OTA. The bracket screws that came with the C6 are too short to attach the ES finder mount. I need longer M4 screws to mount the ES finder.

The 6x30 finder that came with the C6 is OK if all I'm going to look at is the Moon and planets. But for locating and observing DSO and double stars, I want a finder that is erect-image non-reversed with some magnification, in other words, the ES finder.

It may turn out that I only use the ES finder on my C6, 5" Dob, and maybe my 150mm Mak and 8" Dob. One finder that can perform the combined functions of a Telrad and optical finder would be very good for those smaller scopes. I might keep the team of Telrad and 15x70 finder for my 10" Dob. They have worked very well for me at my dark site.

Mike

#94 Jon Isaacs

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Posted 30 January 2013 - 03:26 PM

One finder that can perform the combined functions of a Telrad and optical finder would be very good for those smaller scopes. I might keep the team of Telrad and 15x70 finder for my 10" Dob. They have worked very well for me at my dark site.



That's very similar to what I do. All my Newtonians have straight-through magnifying finders. 8 inches and below, there isn't room for a Telrad so I just use a magnifying finder. The Dobsonians also have Telrads...

Jon

#95 Sarkikos

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Posted 30 January 2013 - 07:10 PM

One feature that most straight-through finders lack that Telrads - and the ES finders - have is an erect-image non-reversed orientation. Most straight-through finders have an inverted image, like the Dobsonian view.

I suppose one thing that the usual straight-throughs have in their favor is that at least they do match the orientation of the main telescope when the main telescope is a Dobsonian. In practice, though, I don't think that this really helps much.

I'd rather that the first line of attack in locating and observing DSO be a finder which has a view matching the natural orientation of my eyes looking skyward. One of the main reasons I picked up the ES finder is that its orientation matches that of the Telrad, printed star charts and my naked-eye.

But I do like a simple, light-weight straight-through inverted finder on scopes when I only intend to observe the Moon and planets. In that case, a little 6x30 straight-through is good enough, and IME & IMO, actually better than a Telrad or red-dot finder. Locating and centering - or recentering - the Moon and planets in the finder is even easier when the finder magnifies a little. And of course, you are looking directly at the object in the sky when you are positioning it behind the crosshairs, so there is none of the frustration that can be caused by having a right-angle finder as the first line of attack.

Mike

#96 Luigi

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Posted 31 January 2013 - 05:26 PM

Holy cow. Lot's of posts...I didn't read them all but in case these haven't been mentioned, I'll add two things:

A blinking reticule helps a lot. I built a little homebrew circuit to accomplish that.

You can look through the Telrad with binoculars. This works better for a SCT, MCT, refractor or similar on mount than it does for most dobs. You can pan around the view with the bins to get the lay of the land and figure out where you are. For trickier star-hops in sparse fields, I use the telrad for very basic aiming, look through it with my bins to see dimmer stars and refine the aim, then use the finder on the scope.

#97 Sarkikos

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Posted 31 January 2013 - 08:10 PM

Hi Luigi,

When I'm at my dark site, I just turn the Telrad way down, almost off. That seems to work well enough. The QuickFinder has blinking capability, but I don't think I've ever used mine at the dark site, only at home for grab-n-go viewing.

I've tried looking through the Telrad with binoculars and also a little monocular. That never worked very well for me. This was on Dobs, though. I even tried rigging up a monocular or half of a binocular behind the Telrad. Seemed like a good idea, but I could never get it right in practice.

This basic idea of wanting magnification and the ability to go a bit deeper with a straight-through illuminated finder is why I picked up the ES finder.

Mike

#98 Greyhaven

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Posted 31 January 2013 - 08:46 PM

I prefer the RACI or even straight through finer to the telrad. On my 12" Dob the angle at which I have to hold my head just is too uncomfortable for me.Plus because of severe inner ear balance issues the placement of my head to use the telrad can set off vertigo, not fun when viewing alone.
The regular finders can be easily aligned during set up before dark I find this very handy. I have 2 telrads and 1 2" riser and would part with them way sooner than I would do without my magnifying finders.
Be Well
Grey

#99 Jon Isaacs

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Posted 31 January 2013 - 08:54 PM

I prefer the RACI or even straight through finer to the telrad. On my 12" Dob the angle at which I have to hold my head just is too uncomfortable for me



What kind of chair are you using?

Jon

#100 Sarkikos

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Posted 01 February 2013 - 09:00 AM

I was able to find longer screws to attach my ES finder to the C6. The ES bracket has four screws for attaching the mount, but the C6 only has two screws available on each side of the focuser. Of course, the ES finder and mount is heavier than the 6x30 setup. If I were to add a 2" VB and diagonal, and/or a Crayford focuser, there might be a problem balancing the C6. I might run out of dovetail. But so far, I'm resigned to the fact that a 1.25" setup is best for this little scope.

The ES finder seems pretty secure when attached by only the two screws. I've held the OTA with ES finder and moved it into various positions. The finder appears to be steady as a rock. Though it would have been a bit easier for grab-n-go if I'd left the 6x30 finder on the C6.

Mike






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