Diagonals

[brrttpaul]

Hi guys been really fed up with this weather, had my new scope (Equinox 80) for three weeks now and still havnt used it yet. Anyway I am told I would need a diagonal to acctually view through it so I was thinking of the skywatcher one that goes with the ED80. but my question is  would I be viewing the right way up or will it be upside down back to front inside out lol. reason I,m asking is I was thinking of putting this on a manfrotto tripod and a gimbal head fo use in birdwatching etc

[Knighty2112]

You need a 45 degree erecting prism to be able to use it as with a normal view, especially for daytime usage. All 90 degree diagonals show a reversed image, so not suitable for birdwatching or terrestrial usage.

Edit: sorry, for your scope you'll need a 2" 45 erecting prism.

http://www.rothervalleyoptics.co.uk/skywatcher-45-erecting-prism-2.html

A lot more expensive than a 1.75"

[brrttpaul]

I thought so thanks very much

[Knighty2112]

I thought so thanks very much

See edit above. You need a 2" one, not as I originally posted up a 1.75" one.

[Dave In Vermont]

I suggest you look for a type of diagonal called an 'RACI' - which stands for: Right-Angle Correct-Image. 'Right-angle' infers a bend of 90° (some are 45° and primarily used for terrestrial viewing in spotting-scopes) and the 'correct-image' that what you see is right-side-up and correct in left-right orientation. This way you don't need to worry about reversing the maps and your view through the finder-scope - they will match.

I also suggest you price mirror-diagonals. Some diagonals employ prisms to bend the entering light-image upwards to your eye. These can be very good. But mirrors tend to be a bit better in their ability to transmit the light-image - say 95% for a prism, and upwards of 99% for a good mirror. A mirror may cost more than a prism, but with a bit of care your diagonal can last a lifetime.

Enjoy!

Dave

[Stu]

You need a 45 degree erecting prism to be able to use it as with a normal view, especially for daytime usage. All 90 degree diagonals show a reversed image, so not suitable for birdwatching or terrestrial usage.

Edit: sorry, for your scope you'll need a 2" 45 erecting prism.

http://www.rothervalleyoptics.co.uk/skywatcher-45-erecting-prism-2.html

A lot more expensive than a 1.75"

That's not strictly true, you can get 90 degree erecting prisms too which show the image the correct way round. In a refractor, the views in a mirror diagonal would be the right way up but left right reversed, confusing but still manageable.

Of course a 45 degree erecting prism is easier the use in daytime when you tend to be looking at much lower angles/altitudes than at night.

Also, there's no reason why you can't use a 1.25" 45 degree erecting prism in your scope as long as you have the 2" to 1.25" adaptor.

[brrttpaul]

thanks guys, its definatly a 2" one is it? as on the equinox theres a smaller section that I have always screwed off tbh  but i was thinkinking that would be the inch an a quarter one. stupid question number two coming up now, so why would anyone buy a 90 degree where it would be upside down? even in space would it not be better viewing right way up? , I know im prob missing something but dont know what lol

EDIT and why is it everything I need is roughly a hundred quid lol the 1"125 were only £37 lol

[Stu]

thanks guys, its definatly a 2" one is it? as on the equinox theres a smaller section that I have always screwed off tbh but i was thinkinking that would be the inch an a quarter one. stupid question number two coming up now, so why would anyone buy a 90 degree where it would be upside down? even in space would it not be better viewing right way up? , I know im prob missing something but dont know what lol

I guess our posts crossed, you can use a 1.25" if you have the adaptor. Cheaper and will work fine.

There's no 'up' in space! The image quality via a good mirror diagonal is better than through erecting prisms so most people opt for the best view.

[brrttpaul]

thanks very much for your help

[Alien 13]

For birding you will probably want to use low to medium powers so I guess a two inch would make more sense.

Alan

[Mak the Night]

http://www.firstlightoptics.com/diagonals/william-optics-125-90-degree-erecting-prism.html

[LukeSkywatcher]

Q: Your scope is new?. Did it not come with a diagonal?. As you know..........for birding etc you will need an erecting prism. Most scopes only come with a star diagonal.

I use an erecting prism for all my astronomy observing. I just cant be bothered with all that upside down/back to front stuff. For watching the birds in the garden etc.....i use 10x50 bins.

[Star Struck]

The equinox comes with a 2" to 1.25" adapter as standard.

So, you can quite happily buy a 1.25 erecting diagonal and not ned to buy anything else.

However, erecting diagonal are not usually recommended for astronomy use.

[Pig]

If your eyepieces are 1.25" then a 1.25" 90 degree diagonal will be fine.

[LukeSkywatcher]

However, erecting diagonal are not usually recommended for astronomy use.

 

Ive been using one for about 5 yrs now and cant think of any problems ive had with it. It came with my 70mm Travelscope but i use it on all my scopes (mainly my 8SE and the travelscope which is now my dedicated solar scope). 

[Pig]

I got strange reflections when I used one

[John]

I got strange reflections when I used one

Me too, for astro viewing.

Fine for daytime use though.

[LukeSkywatcher]

Cant say i have noticed any reflections (let alone strange ones). The one i have wouldnt be the best either because it came with a scope that cost 100 euros. Maybe im just not as critical or even maybe experienced enough to notice such things. Its a bit like CA in a scope. I can see if its there but it doesnt bother me.

[Mak the Night]

I've compared my Amici roof prism diagonals with my standard diagonals and I can't see any denigration of image or other problems. I suppose it depends on your scope or something. Admittedly I want an Everbrite, but for lunar/planetary particularly I can't discern any difference with an erecting prism, apart from the image being corrected. I think erecting prisms were poor quality at one time and gained a bad reputation. That doesn't seem to apply in the 21st century.

[LukeSkywatcher]

Life back in the late 70's/early 80's so so much easier when just about the only scope available was a 60mm Prinz on a German EQ mount and wooden tripod with rack and pinion focuser and no diagonal at all. I think they even just came with one 10mm EP and that was screwed onto the scope and couldnt be removed.

Well that was the very first telescope i ever had. 

[brrttpaul]

My equinox was 2nd hand  not new, but it does have the  1 "125 slot in thing with it along with a white dust cap, the plan is to do a bit of birdwatching as theres no sign of the clouds clearing. I have taken off the adaptor and put a nikon camera on the end and really impressed with the results it was just an after thought acctually viewing through it cheers all

[LukeSkywatcher]

it was just an after thought actually viewing through it 

LOL. 

You sound like many imagers. Some had admitted to owning a scope for yrs and never once actually looked through it.I just noticed your signature. You are indeed an imager rather then observer.

Give observing a try. Its very enjoyable.

[brrttpaul]

I would love to unfortunately  with the weather the way it is and working five days a week the window of oppurtunity is very slim all the time so when i do get the chance the first thing i think of is stick the camera on lol.  Last three weeks have been like living in a tupperware box  just that dull grey view lol

[LukeSkywatcher]

Imagers do seem to be able to grab more time to do what they do than us visual observers. Probably because they can do it remotely from inside. I'm kind of envious, but to do imaging properly involves a lot more gear for me to move about and i really am not in a position to do so. 

[brrttpaul]

Surprised me that comment, I would have thought the other way around lol