Hi guys. I’m extremely new to this stuff and picked up an 200mm (8”)dobsonian reflector 1,200mm focal length ( I’m from Australia, so, you know, metric system) which came with the stock standard 10mm and 25mm plossl eyepieces. I managed to view a bit of Jupiter but not convinced that the scope is properly collimated and the included eyepiece aren’t great to look through so first up I’ve ordered a laser collimator to check the mirrors, but I’m also thinking I should invest in a better eyepiece.
So the question I need help with is, if I could only buy one size eyepiece that would give me decent deep sky viewing but also if I then also grabbed a 2x Barlow, would give me good planetary viewing ie details on Jupiter and Saturn’s rings etc. what would be the most appropriate size?
The other question is, to get viewing of Andromeda would I need to get a focal reducer, or just not really possible with a telescope this size?
Many thanks for any advice.
Understanding Telescope Eyepieces
First, it would help to know what scope you have and if it will accept 2" eyepieces. For Andromeda you would want a low power wide view eyepiece in the 30 to 38 mm range and 65 to 82 degree AFOV range. Here are some examples.
You have given us no information about budget.
A focal reducer is not needed for that scope and is more typically associated with SCTs and Maks. Not even sure it would work in a Newtonian.
The included Plossl eyepieces are likely very good eyepieces, just not as wide as some of the others available today. I would not use a Plossl less than 10 mm in FL because the eye relief gets too short.
Plossls are very good eyepieces – Good discussion
If you could get just one eyepiece and a 2X barlow I would recommend the Baader Hyperion Zoom 8-24. That was my main eyepiece in my 8" and is now my main eyepiece in my 12" Dob.
Your focal length is 1200 mm so the zoom will give you 50X to 150X and everything in between. In a 2X barlow it will give you 100X to 300X and everything in between. That is about all you need other than the 2" low power mentioned above.
This was the eyepiece set I accumulated over 4 years for my 8" and now my 12" Dobs. The bolded ones are the most used eyepieces.
Orion XT8i – 8”/203 mm manual Dob Newtonian, 1200 mm FL F5.9
Resolving power - .6 arc Seconds
AA 70 38 mm 31.5 and 2.2 degrees FOV 2”
Meade 82 20 mm 60X and 1.37 degrees 2”
ES 82 8.8 mm 136X and .6 degrees FOV
ES 82 6.7 mm 179X and .45 degrees
Meade 82 5.5 mm 218X and .37 degrees
ES 82 8.8+2XB 272X and .3 degrees
ES 82 6.7+2XB 358X and .22 degrees
Meade 82 5.5+2XB 436X and .18 degrees
Baader Hyperion 8-24 zoom 50X to 150X
Baader Hyperion 8-24+1.5XB 75X to 225X (My most used 1.25” eyepiece in this scope)
Baader Hyperion 8-24+2XB 100X to 300X
Edited by aeajr, 18 October 2020 - 10:36 AM.