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Seven Ways To Find Things In The Sky - Are there others?

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#101 justfred

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Posted 07 September 2020 - 06:49 AM

One thing that I don't believe has been mentioned is a variation on equatorial setting circles that uses an objects "hour angle". This is the difference in actual time it will take an object to pass through your local meridian. You still have to know the objects declination. Older equatorial mounts had this scale as an option if you wanted to use it. Pretty neat.

 

I like the setting circles on my little Questar. Use the Kochab technique to align in less than two minutes and good enough to have objects in a one degree FOV all night long. Also saves my back from the contortions sometimes associated with equatorial mounts.

 

My other favorite is the point-and-peek method using one of the excellent unit finders available today. Point the scope in the general area and with a little practice your within a couple of FOVs of an object. For the really faint stuff I use this method and then star hop using a good chart.

 

I have to admit that some of today's goto scopes are winning me over. I don't hear near the number of unprintable words I used to hear during an observing session when mounts got kicked, batteries went dead, connections came loose, GPS units went out, sudden unanticipated meridian flips occurred, displays froze, or software just plain quit. 

 

Just to be safe I'm going to try and stay sharp on a couple of manual methods. :-)

 

Fred


Edited by justfred, 07 September 2020 - 06:56 AM.

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#102 aeajr

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Posted 07 September 2020 - 07:53 AM

One thing that I don't believe has been mentioned is a variation on equatorial setting circles that uses an objects "hour angle". This is the difference in actual time it will take an object to pass through your local meridian. You still have to know the objects declination. Older equatorial mounts had this scale as an option if you wanted to use it. Pretty neat.

 

snip...

 

Fred

Fred, 

 

I just went back to read through the discussion.  Several posts in the thread mention something like this.   Let me see if I  have it right. 

 

I am using Deneb as the example.  Let me know if I have this correct.   The image below is from Stellarium.  I have the equatorial grid turned on so things on the horizontal line are on the same declination angle.

 

  • Identify a visible object that is at the same declination as the object you want to see
  • Using Deneb for this example
  • Let time pass
  • The object you want to see will drift into your field of view at a predictable time

    Example – Using an EQ mount
     
  • Deneb is at  RA 20h 41m Dec 45° 16’
  • NGC 7039 is at 21h 10m  Dec 45° 37’
  • They are within ½ degree of each other in Declination which would translate to within ½ degree in your FOV
  • Set Deneb in your FOV and wait 29 minutes. Assuming at least a 1 degree FOV, NGC 7039 will drift into your field of view

Do I have this right?  Remember that I have never used an equatorial mount or RA/Dec coordinates to find objects. 

Attached Thumbnails

  • Deneb - drift method.png

Edited by aeajr, 07 September 2020 - 10:18 AM.


#103 justfred

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Posted 07 September 2020 - 09:03 AM

Yep. You've got it. (oops. see correction in post 108 below)

 

Fun stuff.

 

Fred


Edited by justfred, 08 September 2020 - 12:10 AM.

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#104 aeajr

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Posted 07 September 2020 - 09:28 AM

I am preparing a presentation for our astronomy club on this topic.  Some of the comments and posts in this discussion have helped me better understand these methods.  You have shared new insights on how they can be used and have introduced me to interesting variations, such as the drift methods.

 

The goal of the presentation is to help those new to the hobby.  Many newbies struggle with finding objects they want to see.  Too many drop out in frustration.  My hope is by laying out these 7 methods and helping to make them more approachable I will help some of those who are struggling.

 

In addition, long timers may not be aware of some of the new developments in technology or methodology.  So I can help bring new tools to them. 

 

After a presentation like this there is usually a lively discussion, opinions, and experience sharing that benefits everyone.  

 

In the 5 years I have been involved in astronomy the Cloudy Nights community has taught me so much.  Thanks for sharing your insights and your experience.  I would not be where I am today without your help. 


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#105 aeajr

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Posted 07 September 2020 - 09:45 AM

I really like doing this, but when I find an object, I'm often unsuccessful in trying to identify it.  Like many, I don't  have setting circles on my mounts, or any other useable substitute.  I usually use Sky Safari, but find that it is not precise enough, or shows nothing in the location of the object.  I'm in the process of getting a Nexus with digital encoders set up for my APM big binocular fork mount.  This should solve the problem.

 

Rick

I responded to this earlier but going back through the discussion, I reread your comment and added a slide to the deck.  Thanks for your question.  

 

Using Setting Circles to Identify an Object

 

  • You find something that looks interesting but don’t know its name or designation
  • Using AltAz you can take its coordinates
  • Using RA/Dec you can take its coordinates
  • Now compare to an app or star chart
  • If there is a bright star nearby it can help you zero in on your object's location on the chart or app
  • Some GoTo and PushTo systems have this feature allowing you to ask what object you have in the FOV.
  • Not perfectly precise so you do have to use a little interpretive skill

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#106 aeajr

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Posted 07 September 2020 - 10:30 AM

Recognizing things when you find them.

 

Several posts brought up the fact that you can use the finding techniques to get you to the right spot, but you still have to be able to recognize the target.  

 

Many beginners are frustrated because they can't see the Andromeda Galaxy, for example.   I recounted my frustration over this back in post #75.  The issue was miss set expectations based on pretty pictures in the books, magazines and online.

 

With time and coaching, I learned that what you see in the eyepiece is different from the photos.  Many times, what you see is very much affected by light pollution.  So I recommend resources to newbies that will help them better understand what they are likely to see and what the factors are that affect the image.

 

Aperture - for visual astronomy, aperture is king.   In a small scope a target may be a gray fuzzy.  In a larger scope it may resolve into stars.  I posted earlier about a night spent comparing the view with my 5" Mak and my 12" Dob.   On the planets the difference was not as great as it was on globular clusters. 

 

 

Magnitude vs. Surface Brightness - very important if you are in a light polluted area
https://www.cloudyni...cant-see-stuff/
https://tonyflanders...ace-brightness/
https://www.cloudyni...g/#entry8521236
https://www.astrobuy...com/paul/sb.htm

 

 

 

Astronomy Sketches.

What is wonderful about this is this is very close to what we will see in the eyepieces. They also include what kind of scope was used, what magnification.  These are observing reports.  These will better set our expectations and help us recognize things when we find them.

 

Graphite Galaxy - astronomy sketches
He notes what scope was used.
http://graphitegalaxy.com/

 

DSO Sketches – Mostly 8-10” Newtonian’s  and 80 mm refractor used
http://www.deepskywa...y-sketches.html

 

Planet Sketches
http://www.shallowsk...anetsketch.html
http://www.graphiteg....cgi?lib=databo

 

 

As pointed out several times in this thread, being in the right spot does not guarantee recognition or even seeing anything.


Edited by aeajr, 08 September 2020 - 08:07 AM.

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#107 REC

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Posted 07 September 2020 - 10:41 AM

Pick up a digital Angle Gauge - $30.  Will give you precise Alt which will help you identify the object.

 

I ran a workshop on the AltAz method recently for two clubs.  One of the exercises was to have the group center a bright star, read the angle gauge and then check it on Stellarium or whatever program they were using.  Matched perfectly. 

 

So, if you find something at 36.5 degrees altitude, a little right of Arcturus, you can check your app and identify it.  If you can estimate the Azimuth you can be even more precise.  You can get the AZ by using Arcturus and using FOV of eyepieces, Telrad circles to estimate.  Or you can use a compass or AZ circle on the mount. (see post 24)

 

A newbie who attended the workshop emailemed the next day. He had his scope only a few weeks.  He got up at 3 AM and found Uranus by pegging Mars, then setting the altitude, then sweeping left till he found the blue ball.  I was impressed that he had done that on his own.   He can now find anything in the sky. 

 

Using an angle gauge to help find targets – AltAz coordinates
https://www.cloudyni...y/#entry8120838

You have a lot of good ideas! FYI for the poster, if you are using SS and click on the image, say Jupiter or a star and go down the the battom of the page and click on info, it will give you all the info on the object and direct coordinates at that moment. I have been using it a lot on Jupiter and Saturn lately to see when it will be the highest in my sky for best observing.


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#108 justfred

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Posted 08 September 2020 - 12:01 AM

Oops! So much for my rusty memory... 

 

When using the hour-angle remember that it takes an object approximately 24 hours to move 360 degrees ( there's a small difference but this is close enough). That comes out to (24hoursX60min/hour)/360 degree = 4 minutes of time per one degree of angular separation... Bottom line is that it would take an object 2 minutes to move 1/2 a degree. 

 

Some things are never simple. :-)

 

Sorry for any confusion.

 

Fred


Edited by justfred, 08 September 2020 - 12:24 AM.

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#109 Starman1

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Posted 08 September 2020 - 01:18 AM

Fred,

I just went back to read through the discussion. Several posts in the thread mention something like this. Let me see if I have it right.

I am using Deneb as the example. Let me know if I have this correct. The image below is from Stellarium. I have the equatorial grid turned on so things on the horizontal line are on the same declination angle.

  • Identify a visible object that is at the same declination as the object you want to see
  • Using Deneb for this example
  • Let time pass
  • The object you want to see will drift into your field of view at a predictable time

    Example – Using an EQ mount
  • Deneb is at RA 20h 41m Dec 45° 16’
  • NGC 7039 is at 21h 10m Dec 45° 37’
  • They are within ½ degree of each other in Declination which would translate to within ½ degree in your FOV
  • Set Deneb in your FOV and wait 29 minutes. Assuming at least a 1 degree FOV, NGC 7039 will drift into your field of view
Do I have this right? Remember that I have never used an equatorial mount or RA/Dec coordinates to find objects.
This works with alt-AZ scopes too.
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#110 trapdoor2

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Posted 08 September 2020 - 09:01 AM

Too bad you can't "like" a whole thread. Thanks y'all, I've learned a great deal.


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#111 Rapidray

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Posted 08 September 2020 - 09:38 AM

I agree 100%...there are a couple of great threads that would get that button. Those threads were enough to get me join!


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#112 awmeyer

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Posted 17 November 2020 - 02:49 AM

Just chiming in as a rare kibitzer.  "justfred" introduced in #101 using hour angle.  Elaborated by aeajr in #102 etc., this is described as acquiring something easy (bright star) west of the desired target at the same (or tolerably close) declination, then waiting the proper time interval (difference of right ascension) for the goal to drift in.  

The original concept of a physical hour angle setting circle was to have the equivalent for east-west pointing of the fixed declination circle for north-south.  It was predicated on having sufficiently accurate local sidereal time (R.A. at local meridian) available.  The drift technique is one of several that can be classified as differential offsetting.  Some of the other techniques (e.g. counting FOVs) are in that category.  A fixed hour angle circle on an equatorial mount can be used for absolute pointing.  The latter category has a single zero-point or implicit starting point for the entire sky.  

The advantage of the hour angle circle is that it is fixed to the mount, just like the declination circle.  For permanently installed mounts, once both circles are positioned (calibrated) they are locked down, like with good set screws.  As others have noted, an RA circle must rotate at the sidereal rate, may have to be zero-set at the beginning of each observing session, and that feature makes it vulnerable to being inadvertently disturbed or shifted away from its initial ok setting.  

Here's a partially modern version of old-fashioned absolute pointing with an hour angle circle: 

1.  Look up the current hour angle of the desired target.  I use Orion's "StarSeek 5",  I'm sure any of the night sky apps you all mention provide hour angle.  Just check it's using your observing locality, and the time/date is "now" and updating.  

2.  If GEM, pre-position scope on appropriate side of mount, i.e. scope on west side of mount for rising object (HA <0).  

3.  Set to target declination

4.  Set to current absolute hour angle of desired target.  Note that a minute or two may have passed since you looked up the target's hour angle.  

Optional:  displayed numeric values on little smartphones can be hard to read.   I set a countdown/countup timer app to the current time difference from the target's transit time, so I have an updating large display of its hour angle.  Some timer apps can be set for this by just typing in the target transit time, if it's your local time. 

 

n.b.:  both setting circles can be initially positioned during the day by pointing the telescope at the zenith, where HA = 0,  and Dec. = your latitude.  You can do this pretty well (~1 degree or better) with a good carpenter's level along the tube, or straddling the top opening.  This assumes the polar axle itself is already aligned well enough.

 

n.b.:  for portable telescopes, you can use the HA and Dec circles to set up before sundown, if the telescope and mount can be rotated in azimuth.  Look up the Sun's HA and Dec, set the telescope to those, then rotate in azimuth til the scope is pointed at the Sun.  With care this can be done to about 1 degree precision or better.  


Edited by awmeyer, 17 November 2020 - 02:56 AM.

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#113 Starman1

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Posted 17 November 2020 - 01:27 PM

The simplest finding of objects without any form of computer is on an EQ mount:

1) Go to a bright star near your target, one for which you know the RA and DEC.

Slip the setting circles to read the coordinates of that bright star.

Move mount to RA and DEC of target and there you are.

No electricity of any kind required, just a red LED flashlight.

I found all the Messier objects doing this on my first scope 57 years ago.

2) Offsetting: Look at an atlas to determine how far N or S of a bright star and object is and whether it is E or W.

Go to the bright star.  Move mount in DEC to the number of degrees N or S of the star the object is and lock the DEC axis.

Move scope in RA until the object is found.

Aside: this can also be done by counting eyepiece fields north or south of the star if 1 or 2 degrees is hard to read on the setting circles.

3) Observe a swath of sky with multiple objects by:

--finding the DEC needed to find them all and start west of the objects in the swath.  Lock DEC and move scope to east to see each one in turn.

--or simply wait while the Earth turns to bring each one into view.

--or start east of the objects and scan west.

You need to look at an atlas to find such swaths, but it works very well.  I remember one swath of DEC in Scorpius/Sagittarius with 11 objects in a little over an hour of RA.

4) Looking at an atlas, find targets that are due E, W, N, or S of a naked eye star and point at the star and then scan the correct direction.  LOTS of objects can be found this way, especially

if scanning using a low power eyepiece with a large field of view.

 

All those techniques point out the superiority of the EQ mount over the Alt-Az mount.  I'm a dob user, so am thoroughly familiar with the alt-az mount and starhopping, and I don't think EQ mounts

are very practical for large scopes.  And, thanks to sophisticated digital setting circles, even an alt-az scope can easily find any object.

But using an EQ mounted scope is a practical and easy way to find objects while learning the sky and the use of an atlas.

 

Does that mean I'm a dinosaur?


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#114 aeajr

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Posted 17 November 2020 - 02:08 PM

The challenge with the EQ mount is that it is foreign to those new to the hobby. Not only the hardware, but the language and terms around an EQ mount.

I have been in the hobby since 2015 and I have had no success targeting with an EQ mount.

Likely most newbies first contact with an EQ mount will be similar to mine, working with a poor quality low end model. And they will be trying to do it without someone to help them. Same as me.

The frustration level can be severe and the failure rate high. Perhaps, in the past, EQ equipment was better.

One of my personal goals, after having owned 8 scopes, is to find someone to teach me how to use an EQ mount.

#115 Starman1

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Posted 17 November 2020 - 04:33 PM

This was my first scope at age 12 in 1963 (it was, IIRC, $69.95):

https://astromart.co...ar-jr-newtonian

I think mine had a different name then (Deluxe Space conquerer or something like it), but it was basically the same scope.

Setting circles were cardboard circles attached with rubber grommets to the axes and the pointers were essentially pins sticking out of the mount.

That was about as rudimentary as it gets, but the owner's manual described how to use it to find objects, and I was successful at it, so it was easy to use.

I was new to the hobby, had no adults to help me, and my lowest power eyepiece had about a 1° field.

 

https://www.skyatnig...etting-circles/

Go down the page to "Setting Circles" and read from there.

 

I think what helped more than the mount was the magnitude 6.2+ skies in my backyard.

Finding objects might have been a lot more frustrating in the typical backyard of today, where mag.4.5 or worse is the limit.

 

With inflation, that price is $595.66 today.  And it was, perhaps, no better than today's Celestron Astromaster, which sells for a lot less.

 

Today, a Celestron Omni XLT 102 model can be had for around $500, still cheaper than that 4.25" scope carried forward, that has a dramatically superior CG4 mount, with setting circles with vernier readouts that can be read to 0.1°,

better 4" refractor optics, finder, focuser, etc.etc. You can't buy a new car for $1600, like you could back then, or a cup of coffee for 5 cents (what I paid in the late '60s), so why look at telescopes for the same prices as the 1960s?

$500 today represents fewer days of work for the average worker than $70 did in 1963. 


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#116 aeajr

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Posted 13 February 2021 - 09:47 AM

These methods can be used in combination.

 

For example

 

You can use RA/DEC or AltAz to get you to a good starting point, then star hop to your target.

 

Or

 

You can visually move to a bright star near your target, then use an angle gauge to set the altitude.  Now you sweep over to the target making sure you maintain the angle.

 

I am sure there are other combinations, but these are two that I have used. 



#117 gwd

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Posted 15 February 2021 - 11:02 AM

I sometimes use a star hop method that I call the cross method for finding dim objects.  I pick two pairs of relatively bright stars where the great circle segment between each pair comes within the field of view of my instrument.  Where these segments cross is the location of the dim object.   For example two pairs that I use to find M2 in binoculars is ((α AQR, θ AQL) ,(β AQR, ε PEG)).  This crossing point is easy to visualize with naked eye before pointing binoculars at that point.   

 

As an example of a cross point where the bright star pairs weren't visible to me with naked eyes I've attached a custom chart I created to help me find the variable star SS VIR.    The chart includes a third great circle segment between two naked eye stars to guide my binocular scan to the two pairs of dimmer stars that form the crossing segments.   

 

I wrote an algorithm in SQL to list candidate pairs of stars with respect to a point on the celestial sphere from a database of stars.  I think you could also use the method by examining stellarium or sky safari or paper chart images.   

Attached Thumbnails

  • SSVir.jpg

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#118 gwd

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Posted 15 February 2021 - 11:05 AM

Note to post 117- You might need to download and zoom the SS VIR chart, I made it for my instrument and sky conditions at the time so the segment lines and star symbols are dim. 



#119 aeajr

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Posted 08 May 2021 - 04:32 AM

In the first post I identified one method as plate solving.   The example I used was the Celestron StarSense Explorer which is based on using the camera in a smartphone and plate solving software.

 

The original StarSense Explorer set included 80 and 102 mm refractors as well as 114 and 130 mm reflectors.

 

Seems Celestron is about to release this on the C5 and C6

 

STARSENSE EXPLORER™ DX 5" SMARTPHONE APP-ENABLED SCHMIDT CASSEGRAIN TELESCOPE

https://www.celestro...grain-telescope

 

STARSENSE EXPLORER™ DX 6" SMARTPHONE APP-ENABLED SCHMIDT CASSEGRAIN TELESCOPE

https://www.celestro...grain-telescope

 

It appears this plate solving approach will spread to more of the Celestron line over time.  How long before Meade, Orion and others come out with their own versions? 

 

Will encoder based PushTo systems soon fade away? 

 

How long before a Plate Solving GoTo mount, that does not use encoders, comes to market?  Or is there one out there already?

 

I love the use of technology to help make astronomy more inviting to a larger audience. 


Edited by aeajr, 08 May 2021 - 04:40 AM.

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#120 Jeff Lee

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Posted 08 May 2021 - 07:58 PM

I am lazy. Give me Plate Solving with SharpCap and SkyTools and either of my systems puts anything in SkyTools even on my 224 chip for EAA. The 294 and my other M43 sized chips in the center every time. Sometimes I'm out under the stars, other times looking on the 4K 50". EAA and plate solving is my final solution. I have millions of targets and with EAA no guessing as if they are there or not. As Frank said, I do it my way:)



#121 Tony Flanders

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Posted 09 May 2021 - 05:31 AM

It appears this plate solving approach will spread to more of the Celestron line over time.  How long before Meade, Orion and others come out with their own versions? 
 
Will encoder based PushTo systems soon fade away? 
 
How long before a Plate Solving GoTo mount, that does not use encoders, comes to market?  Or is there one out there already?
 
I love the use of technology to help make astronomy more inviting to a larger audience.


Those are all excellent questions; I have been wondering precisely the same thing. As one practical question, did Celestron manage to get some patent on the technology that seriously inhibits competition, as Canon did for their image-stabilized binoculars?
 

It seems to me that plate solving is the future. Basically, this is star-hopping done fully automatically; the camera/computer combo is imitating how skilled humans do the same thing. But the critical skill here is pattern matching, and that's one of those things that computers do much better than the human brain -- at least when presented with delightfully quantifiable data like the angular distance between stars and their relative brightness.

 

As I (and others) have often said, the great thing about star-hopping is that given sufficiently detailed star charts, it gets you to precisely the right spot -- within arcminutes -- each and every time you do it, no matter how many obstacles are thrown in your path. It may be slow, but it's the ultimate in reliability and accuracy.

 

Likewise, any automated Go To or push-to system that relies on encoders or (heaven forbid!) sensing Earth's feeble and fluctuating magnetic field has inherently limited accuracy. Star positions, by contrast, are the gold standard. They're used by spacecraft to navigate to the Kuiper Belt as well as by astronomers to measure the minuscule fluctuations of Earth's rotation rate. So no other telescope-pointing method can possibly match them in accuracy. Yet everything required to sense a telescope's position by plate solving is built into a modern smart phone. How can you lose?


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#122 Starman1

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Posted 09 May 2021 - 11:17 AM

But a long way, hardware-wise, from matching the accuracy of magnetic encoders when finding a faint object in a crowded field with no bright stars nearby.

It has the potential to revolutionize pointing but there are some problems/barriers:

--sensitivity

--pointing accuracy

--internal computations to overcome inaccuracies in scope construction

All are problems that can be overcome.

Will there be the necessary development in this area for the amateur astronomer?  I'm hopeful.

Magnetic encoders with 1 second of arc sensitivity are available for amateur telescopes now and very affordable.

I think they can be made wireless without too much difficulty.

I suspect the key problem to overcome will be the 3rd one.


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#123 REC

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Posted 09 May 2021 - 04:26 PM

In the first post I identified one method as plate solving.   The example I used was the Celestron StarSense Explorer which is based on using the camera in a smartphone and plate solving software.

 

The original StarSense Explorer set included 80 and 102 mm refractors as well as 114 and 130 mm reflectors.

 

Seems Celestron is about to release this on the C5 and C6

 

STARSENSE EXPLORER™ DX 5" SMARTPHONE APP-ENABLED SCHMIDT CASSEGRAIN TELESCOPE

https://www.celestro...grain-telescope

 

STARSENSE EXPLORER™ DX 6" SMARTPHONE APP-ENABLED SCHMIDT CASSEGRAIN TELESCOPE

https://www.celestro...grain-telescope

 

It appears this plate solving approach will spread to more of the Celestron line over time.  How long before Meade, Orion and others come out with their own versions? 

 

Will encoder based PushTo systems soon fade away? 

 

How long before a Plate Solving GoTo mount, that does not use encoders, comes to market?  Or is there one out there already?

 

I love the use of technology to help make astronomy more inviting to a larger audience. 

Thanks for the ino Ed, I have not been following this Plate method. Is the any videos showing how they work? Can you just buy the mount and put any scope on it? Sounds like fun.


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#124 aeajr

aeajr

    Hubble

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Posted 09 May 2021 - 05:53 PM

Thanks for the ino Ed, I have not been following this Plate method. Is the any videos showing how they work? Can you just buy the mount and put any scope on it? Sounds like fun.

https://www.youtube....h?v=3Hb0x-IdeDs

https://www.youtube....h?v=-0HRfgWit-4

 

Mount, software and license are only sold with a full scope package.


Edited by aeajr, 09 May 2021 - 09:14 PM.

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#125 dave253

dave253

    Vostok 1

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Posted 10 May 2021 - 02:15 AM

I’m glad I learned star hopping in the 80’s. My young eyes could see lots in the vixen 80mm.
Now as an older man, I love the ease of go to. Yep I know where most of the things are, but it’s fun watching a ‘new astronomer’ face when they see it slew to it. 




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