Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4SE

Got a beginners' question? No matter how elementary, our friendly forum community and magazine writers will answer it.

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby Aratus » Mon Dec 04, 2017 7:42 pm

Theoretically eyepieces with a smaller focal length will give you a higher magnification. Unfortunately they restrict 'eye relief' which makes the angle at which you can see anything very small. The older you are the worse it is. As someone in my late 50s, I wouldn't get an eyepiece smaller than a 12mm. If you have young eyes, then go for an 8mm!

The focal length of both these telescopes is 1325 mm. So you could get an 8mm eyepiece and that would give you a magnification of 1325/8 = x165. That magnification is about as large as a 4" will give good results on an average night.
Another way is to get a 2x barlow. This increases the focal length of your telescope by 2, and by definition, the magnification. So if you get a 15mm eyepiece and a x2 barlow you get a magnification of 1325/15x2 which is x177. Slightly better than the 8mm, and with much better eye relief.

You can spend any money you like on eyepieces and barlows, but you probably want to spend something in proportion to the money you spent on the telescope. These are pretty good, and won't break the bank.https://www.firstlightoptics.com/celestron-eyepieces/celestron-omni-plossl-eyepiece.html
and a barlow to go with it.
https://www.firstlightoptics.com/barlows/celestron-2x-universal-125-barlow.html
You can spend more or less than that, and you might be able to get these or similar ones elsewhere. These are just an example. You can get x2.5 or x3 or even x4 barlows, but remember to keep the maximum magnification for a 4" telescope to well below x200, otherwise the image will be dim, and unsteady.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 818
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby EIZO » Tue Dec 05, 2017 3:55 pm

Only what I would use personally, but I don't know what the capabilities are of a smaller scope.

I have a number of eyepieces but mainly use a 9mm, 19mm and 30mm
Celestron Edge 8" Evolution, Esprit 120mm triplet, Sky Tee2, WO Binoviewers, 2" and 1.25" eyepieces, ZWO ASI 178MM camera, Neximage 5, Nikon D4s, D810, Nikkor 70-200 F2.8, Nikkor 14-24, Nikkor 70-200, Nikkor 24-120, Sigma 150-600 Sport
EIZO
 
Posts: 199
Joined: Sun Nov 26, 2017 9:09 pm

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby The Man with the Corrugated Iron Roof » Wed Dec 06, 2017 12:04 am

Using eyepieces and Barlow lenses to boost a telescope beyond its capabilities does not work. I once did just that by using a 60mm refractor with 600x magnification. Venus looked like a comet and the whole image was fringed with blue. SOME telescopes can break the 50x magnification per inch of aperture rule BUT there is still a limit that just cannot be breached.

Unless you want Venus to look like a comet.
How can I be one with the universe when we don't know what 96% of it is.

My website: http://www.philippughastronomer.com/

My blog: http://sungazer127mak.blogspot.com/

Photos: https://www.flickr.com/photos/philippughastronomer/
The Man with the Corrugated Iron Roof
 
Posts: 480
Joined: Sat Nov 23, 2013 1:53 pm
Location: Wiltshire but can be just about anywhere up to 41 000 feet

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby EIZO » Wed Dec 06, 2017 11:02 am

The 50x rule is an old one, and as the above states you can push a scope too far.

The 50x rule is for a good telescope with good conditions,
Celestron Edge 8" Evolution, Esprit 120mm triplet, Sky Tee2, WO Binoviewers, 2" and 1.25" eyepieces, ZWO ASI 178MM camera, Neximage 5, Nikon D4s, D810, Nikkor 70-200 F2.8, Nikkor 14-24, Nikkor 70-200, Nikkor 24-120, Sigma 150-600 Sport
EIZO
 
Posts: 199
Joined: Sun Nov 26, 2017 9:09 pm

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby EIZO » Wed Dec 06, 2017 11:08 am

If I were spending $1000 I would not buy one of these small 4" scopes, I would prefer a dob, 4" is SOOOOOOOO limiting, also you will never be able to use 2" eyepieces.
Celestron Edge 8" Evolution, Esprit 120mm triplet, Sky Tee2, WO Binoviewers, 2" and 1.25" eyepieces, ZWO ASI 178MM camera, Neximage 5, Nikon D4s, D810, Nikkor 70-200 F2.8, Nikkor 14-24, Nikkor 70-200, Nikkor 24-120, Sigma 150-600 Sport
EIZO
 
Posts: 199
Joined: Sun Nov 26, 2017 9:09 pm

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby Aratus » Wed Dec 06, 2017 8:03 pm

There has been quite a lot of discussion about maximum magnification per inch of aperture - some of it quite heated. I think the starting position is 50x per inch. That represents good but not unusually rare conditions. In excellent or superb conditions you can crank up the magnification to well beyond that, but that only occurs once every few years. In 46 years of observing, I've come across that about 10 times. Average conditions are about 40x per inch. However, there is a modicum of subjectiveness in all this. Some people are happier with pulsating, dim images than others, and claim that they can see detail in it. What I say is that there is no harm in trying to 'up' the magnification and see for yourself, but high magnifications isn't where I would start off.

Eizo - As someone who started with a 40mm refractor, and filled 5 years of log book observations with it, I know that a small telescope is far from useless. Now I have a 280mm and 2" eyepieces I see an awful lot more, but I can't say that at the time, I didn't have just as much fun with the 40mm. When you are starting out, any telescope is a great instrument. Of course we couldn't go back to using a smaller instrument, but that's not the position where someone is when they are just starting out.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 818
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby dave.b » Thu Dec 07, 2017 1:44 am

Get a zoom eye piece; 8 to 24mm at around £80 or so from Celestron. Lots of fun to use. Barlow's are a waste of time for visual use, due to the way your eye works, and for a camera you need you use a high quality one that cost a fair bit.
dave.b
 
Posts: 799
Joined: Mon Feb 13, 2012 6:35 pm
Location: Staffordshire

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby Gfamily2 » Thu Dec 07, 2017 3:21 am

dave.b wrote: Barlow's are a waste of time for visual use, due to the way your eye works


I'd be interested to know what you mean by this.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Gfamily2
 
Posts: 453
Joined: Thu Jun 25, 2015 10:38 pm

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby EIZO » Thu Dec 07, 2017 10:15 am

Gfamily2 wrote:
dave.b wrote: Barlow's are a waste of time for visual use, due to the way your eye works


I'd be interested to know what you mean by this.


So would I what a silly comment and without any explanation

It is like saying that using a tele converter with a lens on a camera is pointless when even I do as a Professional photographer but not saying why.

If they had said "loss of quality of the image may occur" then I could accept that but minimal and if they were useless no one would buy them
Celestron Edge 8" Evolution, Esprit 120mm triplet, Sky Tee2, WO Binoviewers, 2" and 1.25" eyepieces, ZWO ASI 178MM camera, Neximage 5, Nikon D4s, D810, Nikkor 70-200 F2.8, Nikkor 14-24, Nikkor 70-200, Nikkor 24-120, Sigma 150-600 Sport
EIZO
 
Posts: 199
Joined: Sun Nov 26, 2017 9:09 pm

Re: Celestron Astro Fi 127mm WiFi SCT or Celestron Nexstar 4

Postby Aratus » Thu Dec 07, 2017 4:32 pm

dave.b wrote:Get a zoom eye piece; 8 to 24mm at around £80 or so from Celestron. Lots of fun to use. Barlow's are a waste of time for visual use, due to the way your eye works, and for a camera you need you use a high quality one that cost a fair bit.


I can't think of any disadvantage in using a Barlow to achieve a desired magnification, as long as the magnification is within the limits mentioned previously. There is a little overall light loss from the use of extra lens, but actually nothing compared to the light lost on a zoom lens! There are pros and cons of most methods, without there necessarily being a overall best choice.
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
Aratus
 
Posts: 818
Joined: Tue Jan 12, 2016 2:17 pm
Location: East Lincolnshire

PreviousNext

Return to Ask a silly (astronomy) question

Who is online

Users browsing this forum: No registered users and 2 guests