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A few ?'s about my new 8" dob

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#1 Haas

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Posted 17 February 2013 - 07:35 PM

I recently posted my 8" dob I got off craigslist, it's the orion XT8.

I caught my first glimpse of the moon tonight, and it was spectacular. Looks like a painting, it was so clear. But, I see that there is a bright star very close to the moon, and found out that is saturn. I tried to zero in on it, but couldn't find it very easily, and gave up before I froze to death out there. I was shivering and couldn't look very calmly anyway.
Here's the questions. Since the moon and saturn were so much straight above me, it made quite a kink in my neck trying to zero in on it through the finder scope. It was suggested to get a telrad (spelling?) scope? Will that make it easier to find things in the finder scope? I could have found it easy with what I have if I didn't have to bend like a snake in order to look through it. Would I be better off with a 90 degree finder scope?

2nd question, I have two eyepieces. A plossl 25mm and a plossl 10mm.
When using the 10mm, the field of view is so narrow, and so is the eyepiece for that matter. Is there any higher magnification eye pieces that still offer the wider field of view?

#2 Haas

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Posted 17 February 2013 - 07:37 PM

Oh, one more thing, if you're trying to find something you see on a star map, but you cannot see it with the finder scope, are you just stuck with scanning the sky until you see it? Not that I'm opposed to scanning the sky for fun, but just wondering if there are any tricks.

#3 Allan...

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Posted 17 February 2013 - 07:45 PM

That wasn't Saturn; that was Jupiter near the moon last night. I have a 9x50mm Right angle finderscope and find it a little difficult to use; plus it dews up too easily. Went back to using the Red Dot finder; not perfect but it works; even though one has to strain the neck a bit. Do more research; ask lots of questions before buying a finderscope. A laser might even suit your needs better.

#4 Haas

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Posted 17 February 2013 - 07:48 PM

Ooops, yeah, I meant Jupitor. :foreheadslap:

#5 Allan...

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Posted 17 February 2013 - 07:51 PM

Hey no problemo. Easy mistake. Im waiting for Saturn to come back to a more "reasonable" hour of viewing, myself. Think it rises after midnight now, sometime; to the East. Ive not seen it yet in my XT8; only got the scope in June of last year. ps: check your mail; I sent you a PM offline.

#6 Haas

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Posted 17 February 2013 - 07:54 PM

Hey no problemo. Easy mistake. Im waiting for Saturn to come back to a more "reasonable" hour of viewing, myself. Think it rises after midnight now, sometime; to the East. Ive not seen it yet in my XT8; only got the scope in June of last year. ps: check your mail; I sent you a PM offline.

Got it and replied already. Thanks!

#7 panhard

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Posted 17 February 2013 - 08:04 PM

Has where do you live? A Telrad isn't a finder scope. Here is what it looks like. telrad

#8 Haas

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Posted 17 February 2013 - 08:07 PM

Has where do you live? A Telrad isn't a finder scope. Here is what it looks like. telrad


Ok, I'm mixing up terminology, but it's still a pointing device, right?

I live in South east Wisconsin

#9 sissyc

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Posted 17 February 2013 - 08:30 PM

Love my telrad. It makes finding things so much easier for me.

#10 Allan...

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Posted 17 February 2013 - 08:30 PM

Herb, Im seriously considering a telrad myself, as the RACI is only So-so in my opinion; cant easily aim it; and find myself looking down the OTA anyways; might as well have a telrad, as I went back to using the RDF, which I was used to (though I do hate the neck pain...lol). Heard that a dew shield for the Telrad changes it in a sense to more manageable for aiming?

#11 Haas

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Posted 17 February 2013 - 08:35 PM

Looking down the OTA is what I'm trying to avoid, if it's even possible. Seems like something that is 90 degrees should be possible, unless of course they dew up like mentioned earlier.

Are laser pointers pretty accurate?

#12 jerwin

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Posted 17 February 2013 - 09:14 PM

You can get a cheap laser pointer off amazon, and scopestuff has a laser finder mount. Sticks on with double sided tape. That's what I use on my dob, then I just hold the button, and position the dob. The green lasers don't like the cold so some people will wrap a hand warmer around it. I personally like a blue laser but apparently some people can't see the blue laser.

http://www.scopestuff.com/ss_sfind.htm

For me, this is the only way to point a dob.

Jim

#13 FlorinAndrei

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Posted 17 February 2013 - 09:16 PM

If you live in the city, a 1x finder such as a Telrad, Rigel QuickFinder or red dot, will be less than useful, due to the light pollution obliterating the guide stars. In that case, a magnifying finder such as a 9x50 is much much more useful because it can reveal the guide stars that would otherwise be invisible.

You could supplement the 9x50 with a green laser attached to the scope (see the accessories section on any vendor's site). Use the laser to quickly point the scope in the general direction, use the 9x50 to fine tune the position.

Under a dark sky, far away from the city, 1x finders such as Telrad can be useful, because then you can see all the guide stars without magnification.

Many people will tell you "get a Telrad" but few understand all related issues.

#14 JLovell

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Posted 17 February 2013 - 09:19 PM

The Telrad is a fancy version of a "red dot" finder. RDF's project an almost holographic reticule of some sort on the sky. The Telrad's reticule is 3 concentric rings of a specific size. All RDF's work by looking along the OTA.

One adventage of the Telrad is the specific size of the rings. There are maps printed specifically for the Telrad such that you place certain easily visible (depending how dark your skies are) objects right on the ring at the same time as certain other stars. Many objects invisible to the naked eye are easily found this way. The rings are also useful for measuring things in the sky when trying to star hop... which is starting at a known point and going a certain distance (measured as an angle, not actual distance) in the direction of another known object.

RDF's can be quite useful, but they are still used by looking along the tube. They are just quite a bit more accurate than eyeballing it because of the reticule.

Green, or to a lesser extent blue, lasers can be useful as well. A sufficiently powerful one can seem to shine all the way to a star. There are special brackets for them that can be adjusted like other finders. I've also seen suggestions to shine a laser in the eyepiece of a finder scope, but I've never tried that.

#15 mman22

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Posted 17 February 2013 - 09:22 PM

Hass, I just got a 6x30 right angle finder scope from Orion. Works pretty well, has a better TFoV than most 9x scopes (7* vs 5*) and so far I have found it very effective (only had it for a week). Dew is not a problem for me here and I have fairly dark skies, so 30mm is more than enough. Haven't used a Telrad, but it has a very good reputation. Herb asked where you live, that will have a big impact on what is best for you to use. Oh, and there are many short f/l eps with better fields of view (I am assuming you are using either a 10mm Orion Sirius or Highlight). You can calculate the TFoV of an eyepiece by dividing the AFoV (listed on the retailers' and manufacturers' websites) by the magnification power (your scope's focal length/eyepiece's focal length). Hey everybody, I got to share some of the knowledge I gained from all of you here! Exciting (even though I feel a little bit like a parrot)!

#16 JLovell

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Posted 17 February 2013 - 09:27 PM

Oh, eyepieces such as the TMB Planetaries or for a bit more money, an Explore Scientific 82 degree eyepiece will be MUCH easier to look through, though the image quality may be SLIGHTLY reduced compared to a plossl.

edit: The TMB's are on sale for $40. https://www.astronom...pieces_c93.aspx

#17 Paco_Grande

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Posted 17 February 2013 - 09:44 PM


2nd question, I have two eyepieces. A plossl 25mm and a plossl 10mm.
When using the 10mm, the field of view is so narrow, and so is the eyepiece for that matter. Is there any higher magnification eye pieces that still offer the wider field of view?


Yes, many choices. That's the main problem with plossls.

Consider these:

https://www.astronom...pieces_c52.aspx

https://www.astronom...ld-eyepieces...

The Explore Scientific are out of stock often because they're on sale and one heck of a value = people want them. You just have to be patient.

And these, a lot of bang for the buck!

http://agenaastro.co...bucket=151&a...

The Agena SWA 2" are also very good for wide field.

#18 NeilMac

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Posted 17 February 2013 - 10:12 PM

make sure you have your finder lined up. Jupiter is a good subject, put it in the middle of the 25mm EP and then adjust the finders screws.

My 25mm is actually my fav Ep, when using my 3X Barlow it has a great magnification with the a great field of view.

#19 Gary Riley

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Posted 17 February 2013 - 10:31 PM

Haas,

If you don't have a lot of light pollution a Telrad 1x finder on the 4 inch riser bracket works very well in helping to get your scope aligned on an object. I would also recommend a right angle correct image finder scope something like an 8x50 or 9x50 to fine tune the object in sight even closer then you should be able to see the object in your main scope. I use one one my Z12 dob and my 4 inch refractor. Love it!

Your 25mm plossl will work pretty well as your low power "finder" eyepiece in helping to locate your objects together with a Telrad and a finder scope. Shorter focal length plossls such as your 10mm do have very small eye relief. You can look at purchasing some eyepieces that will give you larger eye relief something in the 15mm-20mm range that will be easier to look thru. Some examples that are not really expensive would be something like Baader Hyperions, some of the Explorer Scientific eyepieces 68 & 82 degree FOV), Astro-Tech Paradigm ED to name just a few.

Gary

#20 panhard

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Posted 17 February 2013 - 11:14 PM

Ok, I'm mixing up terminology, but it's still a pointing device, right?

Simply put yes.
Allan I use my Telrad while doing my alignment process. Before i had my present dob. I used the Telrad to get close. I then used my 9x50 RACI finder to centre the object. Then use the main scope for viewing. There is lots of good info in this thread read it carefully. If you can see Megrez in the big dipper a Telrad is very useful for star hopping. :grin:
I strongly advise getting one of the risers with a Telrad if you are using it on a dob.

#21 Jeff2011

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Posted 17 February 2013 - 11:30 PM

Haas,

I started by using my iPhone app distant suns and later sky safari. I had a hard time initially reading star charts although I can read them now. I still use my red dot that came with the scope. With the smart phone apps you can size the screen to match your field of view. Point the red dot at a visible star and go from there. One word of warning is that the image in the scope is upside down and backwards. This can be very frustrating at first, but you will get used to it with practice.

#22 Jeff2011

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Posted 17 February 2013 - 11:37 PM

One more thing. Finding objects became a whole lot easier for me when I bought my wide angle eyepiece. It is a 38mm orion Q70 that has a true field of view of 2.2 degrees for my scope. That is twice that of the 25mm eyepiece that came with the scope. To put that into perspective, it is over 4 full moons.

#23 TexasRed

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Posted 18 February 2013 - 12:31 AM

I don't like contorting my neck to try to look up the tube, so I use a 9X50 RACI finder. To get the scope in the general area, I just shine my green laser pointer into the eyepiece of the finder. That gives me a bright green line of light into the sky pointing very close the the same place as the telescope.

#24 Allan...

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Posted 18 February 2013 - 01:12 AM

Texasred, you told us that a while back....and I had forgotten it. I need to do that; get a green laser and try that with my 9x50 RACI, before giving up on it. I could keep it in my pocket if its cold out to avoid the laser cold problems. thanks, Allan

#25 Peshmerga

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Posted 18 February 2013 - 02:38 AM

I have a 9x50mm Right angle finderscope and find it a little difficult to use;


I got an XT8i here, came with a RACI 9x50 finderscrope. First, make sure both scope and finderscope are aligned. If not, align on Polaris, since it's stationary, or any bright star or planet if Polaris isn't available.

My technique to align for the RACI finderscope/find object in RACI finderscope is to stand closely behind the dob. Raise your hand into the air, point at the object of interest, then slowly lower hand till go past the same height as your finderscope. You are drawing an imaginary line that's straight down from the object of interest. Use whatever is in your view, background, foreground to visually mark this line. You then want to move your dob so that the finderscope's tube intersects this imaginary line. Now lower the dob's altitude a bit so you can start scanning from low, or near the horizon. Keep raising the dob slowing and the object of interest should appear in the ~5° view of the finderscope.

A cheap green laser pointer might help. Just make sure it is warm, too cold, the beam weakens. Place the laser parallel against the finderscope base. Beam on, aim, move dob, point at object, check finderscope, should be close.






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