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Finder scopes with exchangeable EPs

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#1 Eliserpens

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Posted 26 March 2020 - 10:03 AM

Hi all - I'm still trying to find the ideal finder for a MN190 (on an EQ mount).  I have Telrad on order but I know that I will also need a magnified finder.  The one on the scope is the stock 9X50, RA non-correcting finder.  I had thought of getting an RACI but then I realized that a finder that allows you to exchange EPs should serve all my purposes as I could get a wide FOV and also zero in on a potential target. 

Is this sensible?  And if so can anyone recommend a model?

Elise



#2 Barlowbill

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Posted 26 March 2020 - 10:12 AM

I am going to suggest that most folks do not feel that is necessary.  If you have a 9X50 RACI, accurately aligned with your scope, you should get close enough with the finder scope to be able to switch to the scope for higher magnification in order to see more than the finder scope.  Use the scope to amplify and not the finder.  Best of luck.


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#3 Jim Davis

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Posted 26 March 2020 - 10:23 AM

If you really want one with replacement eyepieces, try Stellarview.

 

Astronomics also sells one: https://www.astronom...-grey-trim.html


Edited by Jim Davis, 26 March 2020 - 10:28 AM.

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#4 Eliserpens

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Posted 26 March 2020 - 10:50 AM

I am going to suggest that most folks do not feel that is necessary.  If you have a 9X50 RACI, accurately aligned with your scope, you should get close enough with the finder scope to be able to switch to the scope for higher magnification in order to see more than the finder scope.  Use the scope to amplify and not the finder.  Best of luck.

The one I have is NOT image corrected (RA) and a real nuiscance to use on an equatorial mount with all the changes in angles compared to the scope.  Thus, I have to buy one anyway. 

I just discovered that whoever put the Vixen base on the telescope originally (I bought it used) didn't align it correctly.  Thus, when I put a Celestron red dot finder on it was impossible to align :(   I then noticed that while the stock finder I took off that bracket did align, it is grossly skewed to one side for the same reason.  Which begs the question: do you have to access the inside of the OT to fix a new bracket?  So many ifs that spring up... :-\



#5 Second Time Around

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Posted 26 March 2020 - 10:58 AM

Sorry, in haste.

Do a search for Versascope.
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#6 c2m2t

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Posted 26 March 2020 - 11:11 AM

Hi Elise!

I would have to agree with Bill on this one...to a degree. I have a small arsenal of finder scopes nicely stored in my accessory storage that never see the light of day. I have reverted exclusively to red dot finders. The beauty of a good red dot is the ability to scan the sky with both eyes, to guide yourself to your target. Whether you are doing push-to or goto, the result is the same, the red dot can be easily viewed while you are following it across the sky as your scope is moving to its target...this all is happening with both eyes and is very comfortable. As I mention in the POD discussion, finding someone that is using a red dot or telrad and taking it for a test drive is the best way to find a solution to your needs. 

 

The other bonus with the red dot is the  fact they are relatively inexpensive and very compact and weigh just a few ounces. One thing you will want to make sure is that the red dot can be attached in a comfortable viewing position. They tend to be small/compact so they do not stand off your OTA a great distance. The fact is, one can modify the mount by adding extensions. Does your MAK have mounting rings?...the finder can be attached easily to the rings with various fittings. I love working with wood so many of my special fittings are fashioned from oak or plywood depending on the requirement. 

 

There is a third type of red dot type finder by Rigel Systems called a "Quik Finder" and it may better suit your needs.

Here is a link:   https://agenaastro.c...uikfinder.html 

 

Getting back to your present finder...you may want to leave it on your scope in addition to a red dot finder, simply for the wide field view that it will provide. I do that on occasions as well.

 

Good luck!

 

Cheers, Chris.


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#7 c2m2t

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Posted 26 March 2020 - 11:14 AM

The link to Agena appears to be not working so hopefully this works. 

 

https://www.amazon.c...t/dp/B006IJECSI

 

Cheers, Chris.



#8 c2m2t

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Posted 26 March 2020 - 11:26 AM

Hi Elise!

Sounds like you are having some issues with your scope. I am sure there must be someone at the Hamilton RASC that can assist you. I am quite willing to help you in a long distance way if you are comfortable with that. We could chat over the phone while looking at pictures of your telescope. I don't see/hear anything that is too frightening...I am sure we can find a easy solution to the problems. If you wish to contact me away from this forum, check my profile for my email address. 

 

Cheers, Chris. 


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#9 Eliserpens

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Posted 26 March 2020 - 11:36 AM

The link to Agena appears to be not working so hopefully this works. 

 

https://www.amazon.c...t/dp/B006IJECSI

 

Cheers, Chris.

"this item does not ship to Canada' LOL!

I think its in essence the same as teh Telrad...

 

Thanks for the offer to help, much appreciated - but I will have a go by myself first...

ee


Edited by Eliserpens, 26 March 2020 - 11:37 AM.


#10 Eliserpens

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Posted 26 March 2020 - 11:38 AM

Sorry, in haste.

Do a search for Versascope.

Seems to be out of production :-\



#11 c2m2t

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Posted 26 March 2020 - 11:47 AM

Hi Elise!

I sent the link more as imformation. Here is a link to Ontario telescopes:

 

https://www.ontariot...nder_p_422.html

 

Cheers, Chris.



#12 Jon Isaacs

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Posted 26 March 2020 - 11:56 AM

Hi all - I'm still trying to find the ideal finder for a MN190 (on an EQ mount).  I have Telrad on order but I know that I will also need a magnified finder.  The one on the scope is the stock 9X50, RA non-correcting finder.  I had thought of getting an RACI but then I realized that a finder that allows you to exchange EPs should serve all my purposes as I could get a wide FOV and also zero in on a potential target. 

Is this sensible?  And if so can anyone recommend a model?

Elise

 Elise:

 

I think it's very sensible.  This is exactly what I do, a Telrad along with a 50mm RACI finder with interchangeable eyepieces.

 

The Telrad is the best reflex finder available and with it's calibrated 0.5 deg, 2 deg, and 4 deg diameter reticule, it's good for positioning the scope relative to star fields.  That gets me close and very often that puts the object in the field of view.

 

But for more precision, particularly when observing under light polluted skies where not so many stars are visible naked eye, there are just not enough stars visible to accurately point the scope.  The 50mm magnifying finder goes about 4 magnitudes deeper so there's plenty of stars for star hopping.  For me, it's important because while I am often under dark skies, the field of view of the main eyepiece might be less than 1/2 degree so the magnifying finder allows much more precise pointing.

 

As far as the exchangeable eyepieces:  I find there are two important advantages:

 

- Wider field of view, better eyepieces.  I actually modify standard eyepieces with by adding cross hairs.  That way my 50mm RACI has a 6.8 degree TFoV and the eyepiece is sharper across the field than finder eyepieces one can buy.  I also use thicker than standard cross hairs so I can see them under dark skies without illumination.  

 

- Aligning the cross hairs with the axes of the scope and/or sky.  With a standard finder, the eyepiece is fixed so that means the cross hairs are fixed in relation to the scope.  That is OK under some circumstances but very often it causes confusion. 

 

With an alt-az mount, if the finder is at an angle then the finder cross hairs will not be aligned with the horizontal and vertical axes, this makes it confusing to use a chart, particularly an electronic chart that itself will be aligned to the horizontal and vertical axes.  By rotating the eyepiece, I align the cross hairs with the axes of the sky/scope.  I center a star and then move the scope vertically. I then rotate the eyepiece so one of the crosshairs in aligned with that star as I move the scope.  With a standard finder, I actually unscrew the eyepiece to do this. 

 

When I do this, the cross hairs I see on my electronic chart are aligned with the cross hairs I see in the finder so it's a lot easier to figure out what I am seeing and how to move the scope.

 

With an Equatorial mount, it's tricker but you want to align the finder cross hairs with the RA-Dec axes of the scope and then Star Hop using the RA-Dec coordinates of the chart.

 

My 50 mm finder is a StellarVue, AgenaAstro has a similar finder, Astronomics also has a similar finder. 

 

You could also just buy one of the 8x50 GSO RACI finders, they have a 5.6 degree AFoV and turn the eyepiece by unthreading it. 

 

The higher magnification on occasion can be useful but generally it's not.

 

Jon 



#13 Eliserpens

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Posted 26 March 2020 - 12:01 PM

If you really want one with replacement eyepieces, try Stellarview.

 

Astronomics also sells one: https://www.astronom...-grey-trim.html

The Astro-Tech has mixed quality reviews but the Stellarview looks perfect.  I calculate that it has a FL of 203.  I'm going to order that - and it appears they are in stock (things are running out all over)!  Thanks for the tip.

ee



#14 Eliserpens

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Posted 26 March 2020 - 12:11 PM

 Elise:

 

I think it's very sensible.  This is exactly what I do, a Telrad along with a 50mm RACI finder with interchangeable eyepieces.

 

The Telrad is the best reflex finder available and with it's calibrated 0.5 deg, 2 deg, and 4 deg diameter reticule, it's good for positioning the scope relative to star fields.  That gets me close and very often that puts the object in the field of view.

 

But for more precision, particularly when observing under light polluted skies where not so many stars are visible naked eye, there are just not enough stars visible to accurately point the scope.  The 50mm magnifying finder goes about 4 magnitudes deeper so there's plenty of stars for star hopping.  For me, it's important because while I am often under dark skies, the field of view of the main eyepiece might be less than 1/2 degree so the magnifying finder allows much more precise pointing.

 

As far as the exchangeable eyepieces:  I find there are two important advantages:

 

- Wider field of view, better eyepieces.  I actually modify standard eyepieces with by adding cross hairs.  That way my 50mm RACI has a 6.8 degree TFoV and the eyepiece is sharper across the field than finder eyepieces one can buy.  I also use thicker than standard cross hairs so I can see them under dark skies without illumination.  

 

- Aligning the cross hairs with the axes of the scope and/or sky.  With a standard finder, the eyepiece is fixed so that means the cross hairs are fixed in relation to the scope.  That is OK under some circumstances but very often it causes confusion. 

 

With an alt-az mount, if the finder is at an angle then the finder cross hairs will not be aligned with the horizontal and vertical axes, this makes it confusing to use a chart, particularly an electronic chart that itself will be aligned to the horizontal and vertical axes.  By rotating the eyepiece, I align the cross hairs with the axes of the sky/scope.  I center a star and then move the scope vertically. I then rotate the eyepiece so one of the crosshairs in aligned with that star as I move the scope.  With a standard finder, I actually unscrew the eyepiece to do this. 

 

When I do this, the cross hairs I see on my electronic chart are aligned with the cross hairs I see in the finder so it's a lot easier to figure out what I am seeing and how to move the scope.

 

With an Equatorial mount, it's tricker but you want to align the finder cross hairs with the RA-Dec axes of the scope and then Star Hop using the RA-Dec coordinates of the chart.

 

My 50 mm finder is a StellarVue, AgenaAstro has a similar finder, Astronomics also has a similar finder. 

 

You could also just buy one of the 8x50 GSO RACI finders, they have a 5.6 degree AFoV and turn the eyepiece by unthreading it. 

 

The higher magnification on occasion can be useful but generally it's not.

 

Jon 

Great info Jon - though you don't mention which RACI you use :)  And just as you do, my intent is to add a wide angle EP to see more of the sky.  I'm still learning my way around - I know most of the northern constellations now but not nearly to the detail to get around without help - and help is necessary with the contortions of the EQ.  Still, I am determined to master it - with a bit of help. 

 

Do you glue the cross-hairs into the barrel (obviously not touching the glass) and what do you use for material?   

 

I have settled on a Stellarvue F050W2 - it has great reviews and interchangeable EPs.  I guess the unknown is how much capacity there is for reaching focus with other EPs: I may have to find a high FL to match.  Maybe they can help me.

 

I presume I can use the RACI as a finder when I move to photography too...

 

Thanks again

Elise



#15 Second Time Around

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Posted 26 March 2020 - 12:19 PM

Seems to be out of production :-\

This RACI is still available in the UK from Rother Valley Optics at £145.  I have one and can certainly recommend it.

 

https://www.rotherva...inderscope.html

 

"The Antares Versascope is a very versatile accessory. This is a 10 x 60 crosshair finderscope that doubles up as a small guide scope. A very inexpensive way to either upgrade your current finder or get a guidescope attached easily onto your system.

 

The scope features a 6 point adjusting rings for easy alignment to either your object or a guide star. It also has a synta style base for easy attachment onto a wide range of scopes.

 

It also features a front focuser for easy focusing and a wide field 25mm crosshair eyepiece for easy alignment. The 90 degree prism will correct the view for the right way up images.

 

The rear of the finder has a 1.25" twist lock adaptor for the best hold possible. If you unscrew the adaptor, this will give you a T thread so you can attach guide cameras and other accessories while still being able to focus using the front focuser.

 

The scope also has a built on dew shield to battle dew forming on the front of the lens.

 

This really is a brilliant scope and there is nothing on the market that can touch this. Very versatile and very easy to use.

 

Focal length: 227mm"


Edited by Second Time Around, 26 March 2020 - 01:48 PM.

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#16 epee

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Posted 26 March 2020 - 12:29 PM

You might try loosening, but not removing the screws holding the shoe/base to your scope and truing up the alignment as much as you can.

 

I use both a red-dot and an RACI on my 12" Dob. I like the red-dot for general positioning (those stars look a lot alike in a magnified and limited field) and then use the RACI for bringing the object near the center of the main scope's field.


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#17 c2m2t

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Posted 26 March 2020 - 01:36 PM

Hi Elise!

There are so many subtle nuances to all the finders suggested here. I have experience with all of them. The red dot style, be they telrads, Quik Finder or smaller red dots, are the most advantages to zeroing in quickly on a target. What  really separates them from each other is the viewing angle/position. The low profile finders such as the telrad and the more typical red dots can, for some, be awkward to view since the typical installation is directly on the tube/OTA. This requires you to bring your head up against your tube and usually crank your neck a hard 90 degrees to get your eye behind the finder to view the reticle or red dot. The Quick Finder from Rigel gets the reticle into what I think is a more comfortable viewing position, but some may not like the fact it may protrude too far from the OTA and be in a position that it gets bumped. As mentioned in an earlier message in this topic, one can easily fabricate simple inexpensive holders that can put the finder, whichever that ends up being, in the most advantages position for you. All the red dot/reticle finders discussed here are very light in weight.

 

I guess what I am trying to say is, observing is a very personal endeavor and finding out what works best for you is key to a long enjoyment of the activity. If there is a chance to kick tires with someone else's equipment, do it. I did not have that opportunity, so I have made most of the mistakes. grin.gif  

 

I hope I have not confused the issue for you!

 

Best regards, Chris.


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#18 Eliserpens

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Posted 26 March 2020 - 01:45 PM

It's still available in the UK from Rother Valley Optics at £145.  I have one and can certainly recommend it.

 

https://www.rotherva...inderscope.html

 

"The Antares Versascope is a very versatile accessory. This is a 10 x 60 crosshair finderscope that doubles up as a small guide scope. A very inexpensive way to either upgrade your current finder or get a guidescope attached easily onto your system.

 

The scope features a 6 point adjusting rings for easy alignment to either your object or a guide star. It also has a synta style base for easy attachment onto a wide range of scopes.

 

It also features a front focuser for easy focusing and a wide field 25mm crosshair eyepiece for easy alignment. The 90 degree prism will correct the view for the right way up images.

 

The rear of the finder has a 1.25" twist lock adaptor for the best hold possible. If you unscrew the adaptor, this will give you a T thread so you can attach guide cameras and other accessories while still being able to focus using the front focuser.

 

The scope also has a built on dew shield to battle dew forming on the front of the lens.

 

This really is a brilliant scope and there is nothing on the market that can touch this. Very versatile and very easy to use.

 

Focal length: 227mm"

Thanks Steve - sounds terrific.



#19 Eliserpens

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Posted 26 March 2020 - 01:47 PM

You might try loosening, but not removing the screws holding the shoe/base to your scope and truing up the alignment as much as you can.

 

I use both a red-dot and an RACI on my 12" Dob. I like the red-dot for general positioning (those stars look a lot alike in a magnified and limited field) and then use the RACI for bringing the object near the center of the main scope's field.

I'll give that a try.  If it only moves 1 mm I might be back in the game.

 

And what you suggest is exactly what i plan to do.  Should be a bit easir with the 100 fl but harder because of the EQ mount.



#20 Jon Isaacs

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Posted 26 March 2020 - 03:47 PM

The Quick Finder from Rigel gets the reticle into what I think is a more comfortable viewing position, but some may not like the fact it may protrude too far from the OTA and be in a position that it gets bumped.

 

 

I have measured the reticule height of both the Telrad and the Rigel, they're within 1/8 inch of each other. It doesn't look that way but that's how it is.

 

The downside of the Telrad is it's bulkiness, it takes a lot of room. But as a finder, it is the best. The batteries last forever, it has the 4 degree circle, the easiest to view reticule..

 

Jon 


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#21 Jon Isaacs

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Posted 26 March 2020 - 05:29 PM

Great info Jon - though you don't mention which RACI you use smile.gif  And just as you do, my intent is to add a wide angle EP to see more of the sky.  I'm still learning my way around - I know most of the northern constellations now but not nearly to the detail to get around without help - and help is necessary with the contortions of the EQ.  Still, I am determined to master it - with a bit of help. 

 

Do you glue the cross-hairs into the barrel (obviously not touching the glass) and what do you use for material?   

 

I have settled on a Stellarvue F050W2 - it has great reviews and interchangeable EPs.  I guess the unknown is how much capacity there is for reaching focus with other EPs: I may have to find a high FL to match.  Maybe they can help me.

 

I presume I can use the RACI as a finder when I move to photography too...

 

Thanks again

Elise

 

Elise:

 

"Still, I am determined to master it - with a bit of help."

 

I like your attitude.  If there is one virtue, one trait, that is required to be an amateur astronomer, it's perseverance, there are many obstacles and overcoming obstacles, whether it's the clouds, the cold weather, light pollution, bugs, humidity.. it's a big part of amateur astronomy.

 

And having the right equipment to star hop successfully, that is also important.  So many are dismissive of star hopping,particularly under light polluted skies.  If one wants to do it, it can be done.  I do it because I love doing it.  

 

I did mention I use a Stellarvue 50mm RACI finder. 

 

Eyepieces for finders, the short story: 

 

To start out, I would just use the eyepiece that comes with the finder.  I calculate that the eyepiece that came with my SV RACI 50mm provides a 6.0 degree TFoV, that's generous and if you find you want more, that's the time to decide modify an existing eyepiece.

 

The long story:

 

As far as the cross hairs. It's pretty tricky.  First, it only works with some eyepieces. 

 

Eyepieces have a field stop, it's what you see at the edge of the field of view when looking through the eyepiece.   With many eyepieces, if you turn the eyepiece over, you can see that ring.  It's at the focal plane of the eyepiece and since you want the cross hairs to be in focus, they must be attached to the field stop.   Not all eyepieces have field stops that can be seen or that are accessible.  That's the first requirement.

 

The second requirement is that the field stop be wide enough to glue to.  Eyepieces that maximize the field of view have very large field stops, just a fraction of a millimeter narrower than the barrel, there's not much to glue to.  And the diagonal of a finder doesn't have the full 27mm of clear aperture to avoid vignetting.  A field stop of about 25mm is about right about right, enough to glue to, not to wide to vignette.  

 

The third requirement is that eyepiece must focus in the SV finder.  

 

And finally, the eyepiece needs to be reasonably well corrected in the F/4 finder.  

 

Such eyepieces are expensive.. From what I can see, I I think the 20mm Explore Scientific 68 degree would be about the best choice.  I would provide a 6.5 degree TFoV at 10x, it has a 22.8 mm field stop and should be quite sharp at F/4. But it costs $152.. 

 

When I decided to do this, I had an old 24mm TeleVue Wide field that had seen better days and so that is what I used.  It has a near perfect 24.7mm field stop so it provides a 6.8 degree TFoV.   

 

I use 0.004" hard brass wire for the cross hairs. I have a large stock of it and can slip some in an envelope and send it if need be. 

 

Jon


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#22 Eliserpens

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Posted 26 March 2020 - 06:56 PM

Wish CN had a <3 symbol!

 

That's very helpful indeed.  I'll have another think when it comes of course - probably Monday (I paid a little extra for fedex, but never imagined it would be that fast!).  I have to play with it for a while, once I have the telrad then it should be easy to get to know the finder and then to the scope.  Sort of like star-hopping....

 

I did find a couple of new Messiers without any finder: M35 and M41 - both were spectacular even with the 31mm, so I must be getting a bit better with the vagaries of the scope mount.

 

ee


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#23 Jon Isaacs

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Posted 26 March 2020 - 07:28 PM

Wish CN had a heart.png symbol!

 

That's very helpful indeed.  I'll have another think when it comes of course - probably Monday (I paid a little extra for fedex, but never imagined it would be that fast!).  I have to play with it for a while, once I have the telrad then it should be easy to get to know the finder and then to the scope.  Sort of like star-hopping....

 

I did find a couple of new Messiers without any finder: M35 and M41 - both were spectacular even with the 31mm, so I must be getting a bit better with the vagaries of the scope mount.

 

ee

:waytogo:

 

Elise:

 

One technique for finding objects with an EQ mount is using a RA or Dec sweep.  

 

Using a chart, either paper or electronic (I like SkySafari on a tablet), you find a brighter star that has nearly the same RA or Dec as the object that's relatively close to the object.  Then, you find the star in the finder and then swing the scope in only one axis until the object appears in the field of view.

 

One thing about star hopping, the more you do it, the better you get. When I was first starting out, I would find the same objects night after night as practice and also just because I loved looking at them.

 

Jon

 

Jon


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#24 kfiscus

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Posted 27 March 2020 - 12:11 AM

The OP has found a nice, modern, high-end answer.  Here's another option for finders with interchangeable EPs, but one that requires patience and then modification...

 

University Optics (UO) used to make very nice finders that had real focusers and interchangeable .965" dia EPs.  I have one that has a rack & pinion focuser and have another with a helical focuser.  Both are nice but heavy.  I got the r&p one (sold by Orion) in 1983 as an upgrade for the stock 6x30 finders sold on orange C-8s.  I bought the helical focuser model (also Celestron orange) used about 3 years ago.  These finders came with bases that are heavy and old-school, bases that often need adapting or replacement.

 

These finders hardly ever come up for sale on the used market, which to me means that their owners love them.

 

(In the included photo, the Orion's OTA has been wrapped in flocking felt to hide the faded orange and kill reflections.)

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Edited by kfiscus, 27 March 2020 - 12:54 AM.

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#25 Eliserpens

Eliserpens

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Posted 27 March 2020 - 07:11 AM

One technique for finding objects with an EQ mount is using a RA or Dec sweep.  

 

Using a chart, either paper or electronic (I like SkySafari on a tablet), you find a brighter star that has nearly the same RA or Dec as the object that's relatively close to the object.  Then, you find the star in the finder and then swing the scope in only one axis until the object appears in the field of view.

 

One thing about star hopping, the more you do it, the better you get. When I was first starting out, I would find the same objects night after night as practice and also just because I loved looking at them.

 

Jon

Thanks again, that makes sense and is a great way to get used to the mental concept of equatorial scanning.  I've been returning to Orion each night, simply because it has so many large marker stars that you can orient yourself just using the scope.

ee
 


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