Eyepiece View Issue

[Greg6498]

I’m in a bit of a quandary. I have 2 scopes, a Skywatcher Evostar 80mm and a Skywatcher 8” Collapsible Dobsonian. Both are good scopes. The problem is when using the the refractor to view planets the image is tiny. It’s clear, but tiny. Haven’t tried the Dobsonian yet for planets but probably the same result. Is there any way to make the image bigger? I’m using a 6.7 eyepiece now. Please excuse me if this is dumb question LoL!

[banjaxed]

I have an 8" dob and while the planets are not huge I wouldn't call them tiny either.

Give your dob a try you might be surprised.

[laudropb]

The magnification is given by dividing the focal length of your telescope by the focal length of your eye piece. The focal length of your dob is twice that of your refractor, so the image of the planet will be twice as big in the dob. The image of the planet will not be huge but the resolution given by the larger aperture will allow you to see plenty of detail if the seeing conditions are good. The longer you spend viewing the more you will see, so you have to be patient.

Edited July 20, 2019 by laudropb

[Greg6498]

13 minutes ago, laudropb said:

The magnification is given by dividing the focal length of your telescope by the focal length of your eye piece. The focal length of your dob is twice that of your refractor, so the image of the planet will be twice as big in the dob. The image of the planet will not be huge but the resolution given by the larger aperture will allow you to see plenty of detail if the seeing conditions are good. The longer you spend viewing the more you will see, so you have to be patient.

Thank you! That makes perfect sense! I’ve just never tried the dob on planets so I’ll give it a go!

[Sunshine]

I remember how chaffed you were about that dob when you first got it, that’s a sweet little light bucket!

[Greg6498]

16 minutes ago, Sunshine said:

I remember how chaffed you were about that dob when you first got it, that’s a sweet little light bucket!

Haha Sunshine! You are so right! If Amateur astronomy has taught me one thing over the last year it’s patience! My learning curve has been big. I’m really glad I kept the dob and didn’t sell it! Now that I understand more about optics (from all of you!) I think selling would have been a big mistake! At least I try to learn from my mistakes, LoL!

[Alan White]

Give it longer than a year Greg and it will teach you more than just patience.
You will develop the patience of a saint after another year.
I have no idea how the weather in Lexington, USA compares to Thundersley, Essex, UK, 
but living where I do the weather tests the Patience of a Saint sometimes.

Your scope mix sounds great, refractor for nice pin sharp tight stars,
Dobsonian for the fainter or bigger objects.
I own a Vixen ED103s Refractor and a 10" OOUK Dobsonian, this has taken a number of scope upgrades to get here.

[Greg6498]

2 minutes ago, Alan White said:

Give it longer than a year Greg and it will teach you more than just patience.
You will develop the patience of a saint after another year.
I have no idea how the weather in Lexington, USA compares to Thundersley, Essex, UK, 
but living where I do the weather tests the Patience of a Saint sometimes.

Your scope mix sounds great, refractor for nice pin sharp tight stars,
Dobsonian for the fainter or bigger objects.
I own a Vixen ED103s Refractor and a 10" OOUK Dobsonian, this has taken a number of scope upgrades to get here.

Thanks Alan! Astronomy has certainly helped me with my frustration levels LoL! Sunshine was right. When I first started I was pretty frustrated but now I’m taking it in stride! I’ve had some really good nights and some really bad ones but now when they go bad I just pack up and look forward to another night! Everyone’s support here is a huge help!

[Sunshine]

Giving up that dob would be a shame, it will provide you with years of exciting nights still to come.

[Sunshine]

4 hours ago, Greg6498 said:

Thanks Alan! Astronomy has certainly helped me with my frustration levels LoL! Sunshine was right.

I'm sorry Greg6498, maybe I used the word "chaffed" wrong, I meant to say I recall how excited you were, I hear my British buddy throw that word around and maybe every time he says "im so chaffed" I understood he's excited about something when maybe it means one is not so happy lol.

Edited July 20, 2019 by Sunshine

[Greg6498]

12 minutes ago, Sunshine said:

I'm sorry Greg6498, maybe I used the word "chaffed" wrong, I meant to say I recall how excited you were, I hear my British buddy throw that word around and maybe every time he says "im so chaffed" I understood he's excited about something when maybe it means one is not so happy lol.

Haha Sunshine you are right! It means stunned or impressed! It also can mean teasing What I got frustrated with was constantly having to reorient the dob to keep everything in view! Left is right, up is down and it was making me crazy! I found later, with a little practice, it got much easier! LoL!

[Greg6498]

So, all...tonight I’m taking the dob out for a planet viewing on Jupiter and Saturn and, hopefully, a few Messier objects if the clouds cooperate!  

[Alan64]

If the seeing conditions are good, then that 80mm refractor can approach 100x per inch of aperture, which would be 300x.  You could certainly make use of that for the Moon, but let's be a bit more conservative when viewing the planets, at, say, 200x...

600mm ÷ 200x = a 3mm eyepiece

If it were myself, I would combine a 9mm eyepiece with a 3x-barlow, for a simulated 3mm, and for a power of 200x.  The planets, particularly Saturn and Jupiter, put on a fine show at that power.  

There are also eyepieces of those shorter focal-lengths, and with barlowing elements built in, if you'd rather not use a dedicated barlow; for examples...

https://agenaastro.com/explore-scientific-52-deg-series-eyepiece-3mm.html (200x)

https://agenaastro.com/bst-1-25-uwa-planetary-eyepiece-2-5mm.html (240x)

https://agenaastro.com/agena-1-25-dual-ed-eyepiece-3-2mm.html (188x)

https://agenaastro.com/vixen-2-4-mm-hr-eyepiece-37134.html (250x)

This high-power zoom ocular is quite popular...

https://agenaastro.com/televue-1-25-nagler-planetary-zoom-eyepiece-3-6mm.html (100x - 200x)

...and a bit costly.

Edited July 21, 2019 by Alan64

[MarsG76]

The 6.7mm EP should give you around 140X magnification on the 8" dob.. the size should be a OK size but a 3 or 4 mm eyepiece should give you a nice good size on the main planets.

 

[Ricochet]

3 hours ago, MarsG76 said:

The 6.7mm EP should give you around 140X magnification on the 8" dob.. the size should be a OK size but a 3 or 4 mm eyepiece should give you a nice good size on the main planets.

 

1200/6.7=179X

Depending on atmospheric conditions this could be the ideal magnification. In fact this year I usually have to be below that due to the low altitude of the planets. 

[MarsG76]

1 hour ago, Ricochet said:

1200/6.7=179X

Depending on atmospheric conditions this could be the ideal magnification. In fact this year I usually have to be below that due to the low altitude of the planets. 

I guesstoemated around f5... but yes... seeing is crucial if high power is craved for.