148 replies to this topic

[Nightskyman]

Any advice on viewing the planets using a 8” dobsonian and which eye pieces and magnifications I should use?

[Nightskyman]

I should have added, budget friendly on the eyepieces and are either a Barlow or zoom lens worth consideration? If so, how much would image quality suffer?

[Jim Waters]

First of all what's the scope?

[Keith Rivich]

I should have added, budget friendly on the eyepieces and are either a Barlow or zoom lens worth consideration? If so, how much would image quality suffer?

What is your current equipment? 

[tcifani]

Agree with Jim and Keith above, but an 8" Dob could be great for planetary.

[KWB]

Nightskyman

 

If you don't mind the short eye relief your 10mm plossl will work just fine. It has enough on axis quality to serve your purpose. It will give you 120X. If the sky is steady this telescope can handle a lot more magnification. A 2X barlow would increase the magnification to 240X and you would be impressed with the view.

[mikemarotta]

Which eyepieces to you have now? Make and model?  Generally a Ploessl (Plossl with an umlaut) is the basic design type though some better instruments such as yours come with less sophisticated K=Kellner or H=Huygen or MRA = Modified Ramsden designations. 

 

An 8-inch reflector is a serious instrument and will be with you for many years. So, an investment in a better eyepiece will return value over time.  It depends on your budget, of coure. Overall, look to the 82-degree eyepieces.

 

TeleVue is easily the top of the line and they have several lines. They do not sell directly. But their website provides important, detailed specificaitons. https://televue.com 

 

Here, Astronomics is the sponsor of Cloudy Nights. They sell Tele Vue and other brands.(Their brand is Astro-Tech.)

See here, sorted by price low to high

https://www.astronom...464&order=price

 

How long have you been observing?

 

Best Regards,

Mike M.

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Edited by mikemarotta, 20 November 2022 - 08:23 PM.

[Nightskyman]

Scope is a Celestron StarSense Explorer 8 dob

[Nightskyman]

I am just beginning and it came with a 25mm Ploessl. Wondering if either a 2x barlow or a zoom eyepiece may benefit with too much loss of image quality.

[KWB]

A GSO type shorty barlow will not reduce the image quality.

[Bean614]

Why do you have 2 Identical Posts going? Same Exact Question.

[ngc7319_20]

A 7mm 82 degree eyepiece would give about 170x which should give nice views in average seeing conditions.  The wide 82 degree field would help in manual tracking of the planet.  That would be my first choice.

 

https://www.astronom...5-eyepiece.html

 

A 10mm would be good when seeing was below average.

 

https://www.astronom...5-eyepiece.html

 

On the very best nights you could use these two with a 2x Barlow and that would put you near the maximum useful power for that scope.

 

To get the best planet views, you will want to get the scope cooled to ambient temperature.  Maybe leave it outside for a couple hours before observing. 

 

Good collimation of the mirrors will also help -- read up on that.

 

Nights with steady temperatures (not dropping rapidly) tend to give steadier views.  Avoid windy nights -- these have poor seeing and the scope may shake or vibrate.

[dave253]

The budget zoom eyepieces work well, I have the 8-24mm.

[Chilihead]

My first 20 years was with an 8" Dob, and my primary interest was planets.

I used Orion Expanse eyepieces which don't receive nearly enough love. They are fantastic for the price. I sold the Dob to a friend but kept the Expanse EPs to use with my refractors for terrestrial viewing.

[warpsl]

After using my 6 inch achro for the last 20 years,I grabbed a second hand 8 inch f6 dobsonian for a change. The price was cheap,so I thought it's performance would be too.the last few nights have given me the best false colour free views of Jupiter I have ever had.forget about plossls,you need eyepieces with at least 60 degrees a f o v so you have more drift time.my pentax 8.5 xf gives me 141x.my 6mm ortho works good to,but the a f o v is to narrow.i now need a pentax xw7.another thing you can do is put some baffles inside the tube.i used stick on foam weather/draught strip's.get the ones half inch thick.just stick them on the inside in a circle pattern.its easier than making them.

[JohnBear]

If you are  new to astronomy and want 'budget EPs' that are noticeably "better than factory Plossls" for F6 (and up) scopes I highly recommend the Svbony 26mm & 10mm aspherics (not the 4mm).  They are my everyday, startup and alignment, EPs on most of my telescopes. I keep several sets of these handy.  

 

They worked very well on my 8" Dob & SCTs.. They provided avery good frame of reference regarding EP specs to help me discover what was really important to me when buying higher end EPS.

 

Note that very clear and calm nights are required to get the best out of expensive EPs (where newbies actually cab see the differences in good v excellent EPs).  

 

The primary planets are out (near opposition) right now - so make  the most of what you have before they sail away to the other side of the Sun! .  Most name brand zooms ($50-90) are quite good also and can show you a lot about EP specs also.

Edited by JohnBear, 20 November 2022 - 09:50 PM.

[Nightskyman]

I found a kit for $99, Apertura, that has a 2x Barlow and a 15, 32, and 40. They have eye reliefs of between 15 to 22mm. They are Ploessl. The scope also comes with an included 25mm. Would this work to get started and what size should I purchase next?

[Dave Mitsky]

I never recommend buying eyepiece kits.  In this case, the 32 and 40mm eyepieces will produce the same true field of view, with the 40mm having a small apparent field of view.

[Tony Flanders]

An 8-inch Dob is superb for viewing the planets, assuming that the collimation is spot-on and it's well cooled.

 

On mediocre to average nights 120X is a good magnification. On better nights, you can usefully go as high as 180X. On truly outstanding nights you might benefit from 240X.

 

Specific brands don't really matter; they're kinda all the same, as far as I'm concerned. The most important considerations are eye relief and apparent field of view.

 

For my purposes a 10-mm Plossl has usable but somewhat annoying eye relief; I have to hold my eye quite close to the glass to see the entire field of view. That's true of all simple eyepieces, ones with 3 or 4 individual elements.

 

For focal lengths less than 10 mm I find simple eyepieces nearly unusable; my eyelashes brush the glass every time I blink. Two solutions are to use a Barlow lens together with a simple eyepiece of longer focal length (e.g. a 2X Barlow with a 12-mm Plossl) or to buy a special eyepiece with long eye relief -- which in fact has a built-in Barlow.

 

A 2X Barlow plus an 8-24 zoom allows you to fine-tune the magnification to suit the conditions -- very handy. And most 8-24 zooms have excellent long eye relief.

 

As for apparent field of view, the wider it is, the less often you will have to move the Dob to keep the planet in the field of view.

[Corbetto]

I have the 10" version of this scope and to get started, I picked up the Svbony 8-24mm zoom and the Celestron Omni 2x barlow. I've been using these for the last month and have no complaints. I'll be expanding to dedicated eyepieces shortly as I've found that with night time temperatures dropping below freezing, turning the zoom becomes more difficult. That aside, it's a pretty good budget zoom.

[sevenofnine]

The Celestron 8-24mm zoom is one of the best bargains in this hobby IMO. It's very good for planets in an 8" Dob. The advantage of using a zoom is that it allows you to test the "seeing" without having to change eyepieces. I will often use it with a 2x barlow or focal extender. This changes the power to a 100-300x zoom. Of course, most nights the higher powers are very soft but occasionally outstanding. Patience is key here. Good luck! 

 

https://www.bhphotov...Wide_Angle.html.

[rhetfield]

Since the OP's scope is an F5.9, I would not go shorter than about 4.5mm on eyepieces for planets - about 260x.  Shorter than 6mm on that scope and the image will start to get dim and grainy.  Mars, Saturn and the moon will still look decent with the 4.5, but Jupiter probably will not. 

 

As others have noted, short plossls have short eye relief.  The paradigm eyepieces sold by astronomics is a good mid priced eyepiece series.  So are the somewhat more expensive x-cel series.  Avoid the 18mm in both series.

 

Note that atmospheric conditions on most nights in many places will not cooperate with magnifications much above the 150-200x range. Many people will use barlows to go above that range to reduce the number of eyepieces - Going above 200x is a rare treat.  Zooms are good for that too.  

[Dave Mitsky]

Astro-Tech Paradigm Dual ED series  -  https://www.astronom...iece_series=478

 

Celestron X-Cel LX series  -  https://www.astronom...iece_series=490

 

[Dave Mitsky]

Cloudy Nights members get a small discount from Astronomics.

 

https://www.cloudyni...y_discount.html

[CHASLX200]

If the scope has super good optics and you have super steady skies then 450x no problem for the planets.  Most times around 250x to 300x will be best.