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Help with star hopping


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Can anyone give me a few pointers (no pun, honestly) so help me with star hopping? Specifically distances-minutes, arc minutes etc? I get the theory of it but struggling with putting it into practice when looking at the sky and how to judge when it gone the right distance from a certain landmark. Thanks in advance!

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I suppose there are many ways of doing this - you sort of settle into something that suits!  I use Stellarium with the concentric circles (4, 2, and 0.5 deg) over the view.  Then knowing what field of view I have in the eyepiece being used, I move about the sky by comparing what I see with what's on Stellarium.  It's best to use a low mag/wide angle EP first, then up the mag when on target.

A Telrad finder with similar circles (reticle) is also useful.  As too is a Sky Atlas with an acetate sheet with those circles again.

As far as this goes, you only need bother about degrees of sky.  (A degree is 60 minutes, or minutes of arc, or arcmin, and a minute is 60 seconds or arcsec.)

Doug.

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Hiya,
I tried several ways to master star hopping but I eventually settled on the method of selecting an area of the sky and familiarising myself with it, eventually I knew what stars I was looking at and could then reference the distances between them from charts etc...
To actually measure them whilst observing would require some kind of aid, maybe an eyepiece with a built in scale or even some kind of electronic gadget.

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my method isn't very accurate: I start with an easily identifiable star then knowing that my widest EP is about 2 degrees, stick it on the edge and then work out where the next bright star is and repeat until I'm somewhere near - I look for patterns that I can identify in my atlas/map as I go.

some dsos, that I'm familiar with, such as M31, M13 & M57, I can get to with the telerad

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This is what helped me with the distances. I have a 2.25 degrees EP (32mm)so it's close to 2 degrees has illustrated by the blue circle on my atlas subdivisions. I start with that, it's rough but it's enough for me.

for example, my 18mm EP is 1 degree TFOV so half the blue circle represented my 32mm ep. After you can try to figure out minutes and seconds while looking inside the EP. That's why I keep the infos of my EPs on the top of my log sheet, to be able to access easily the TFOV of all my EP.

To the right, the infos to roughly measure with the hand pointing the sky really useful to memorize.

:happy10:

The text is impossible to see for the right part but the distances are: 1 - 5 - 10 - 15 - 25 degrees, with the arm extended towards the sky.

17hy7VZ.jpg?3

Basic theory on Degrees minutes and seconds, (just in case)

http://zonalandeducation.com/mmts/trigonometryRealms/degMinSec/degMinSec.htm

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Hello Doug,

you can use Cartes du Ciel to make finder circle maps. Cartes du Ciel (Skychart) is free.

 

Step1: Use menu > setup > display >  finder circle (eyepiece) to enter your finder's field of view. 

CDC-display-finder.png

Enter the size in arcminutes. My finder is 5.4° or 320 arcminutes. You can also add your eyepieces.
You get more than one concentric circle by clicking more than one button green.

 

step2: Right-click on the map

new circle.png

From the from the context menu, select Finder circle and use the option 'new circle' to add a circle. After a few circles you can print the map.

Found 1.png

It is probably a good idea to use nested circles and include your largest view eyepieces to help you get even closer to your target.

 

Happy star hopping. I hope you find your targets.

 

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I find Sky Safari on iOS brilliant for helping with star hopping. You tell it what eyepieces and scope you're using and it can superimpose a field of view onto the map (similar to the screens above). You can view the stars the right way up (good for binos and RACI viewers), or reflect/rotate the view (to match what you see in a refractor/reflector). Set the red night vision mode on and turn down the brightness of course. A low power and/or wide field eyepiece really helps. I generally avoid hopping to the next star if it's too far away to be in the same field of view as the current star (and instead find a landmark between the two that I can latch onto). With practice it gets easier. Hope this helps and good luck!

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1 hour ago, Size9Hex said:

I find Sky Safari on iOS brilliant for helping with star hopping. You tell it what eyepieces and scope you're using and it can superimpose a field of view onto the map (similar to the screens above). You can view the stars the right way up (good for binos and RACI viewers), or reflect/rotate the view (to match what you see in a refractor/reflector). Set the red night vision mode on and turn down the brightness of course. 

This sounds good-i have any safari on my phone but can't seem to find out how to get this function on, can't find it in settings.

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I've just had a quick look. There are quite a lot of features in SS! In the settings menu, the display and the equipment sub-menus allow you to enter your kit list and choose which of this kit you want to see as field-of-view circles. Back in the regular view of the stars, tap in the top right of the screen and you'll see a new menu appear with the options to flip/rotate the view. Brightness is just through the standard iOS brightness menu rather than in SS.

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First I use a red dot finder to set the scope on the correct finder star. Since I have a detailed atlas (IDSA) and a 50mm RACI finder, I hopp further by reading bright or medium bright stars in my atlas towards the object and move the finder scope until I see them in there. This works for me. In my small 30mm finder this was more difficult.

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I use a specific set of guide stars that work best for me and work from both memory and a short indoor session with Stellarium over viewing the nights options. If attempting new objects I create rough cheatsheets and try not to use them and keep things dark, that's why I refer to them as cheatsheets. I typically use three scopes set up to cover a range of magnification so I stay observing and not fiddling in the night and most often debrief with some study on the objects observed and consider it part of the session. Sometimes when there is little time or an unexpected opportunity becomes available I run on experience, intuition and some uneducated bumbing but I'm in the dark so it goes unnoticed...

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I think I would be wise to get a star atlas-had anyone got any experience of the 'sky and telescope pocket sky atlas' if so is it any good and worth getting? I already have turn left at Orion.

 

I'm also still struggling with areas in the sky-how big is a degree etc? I think i read somewhere that if you hold your finger up at arms length then this covers 1 degree and if you hold your first up it covers 10 degrees? 

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The Pocket Sky Atlas is excellent - detailed maps, bound for easy use, bursting with detail, and indexes of constellations, objects by category, Messier, Caldwell.  Even extra detail for Orion, Pleiades, and the Virgo Cluster.

I made a clear acetate sheet with circles of 5, 2, and 1.5 degrees for mine.  I place it over/around targets to get an idea of what is likely to be in the EP.

Doug.

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56 minutes ago, popeye85 said:

Do how do I go about working out the FOV I'm getting in my ep's?

To arrive at the true FOV divide the apparent FOV for your eyepiece by the magnification. To know your magnification divide the focal length of your telescope by the focal length of your eyepiece.

An example will make this clear:- I use a S/W 150 that has a focal length of 750mm, using a 10mm eyepiece gives a magnification of 750/10=x75. Say the eyepiece has an apparent FOV of 50 degrees the true FOV is 50/75=.666 degrees. 

HTH.

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LoL .... yes it never ends :happy7: Here you go this link will help, there is an explanation at the bottom of the page for each term.

On some eyepieces the hole in the ring that holds the eyepiece glass in place is smaller than the barrels inside diameter thus it becomes the restrictive element. (field stop)

A quick word of warning ...do not unscrew the barrel of the eyepiece to measure the field stop unless your familiar with the eyepiece design as all the glass may come tumbling out. As a rule of thumb the field stop will be approximately 1.25" or 2".

http://www.televue.com/engine/TV3b_page.asp?NoBack=True&id=212&plain=TRUE&focal_length=400&fl_unit=mm&aperture=80&a_unit=mm&fratio=f%2F5&_2in=yes&Ethos=TRUE&Delos=TRUE&title=&sortby=SortTrueField&SUBMIT1=CALCULATE#.VUSBmblFAqQ

 

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