NexStar 6SE Accessories and Upgrades Advice Sought

[greglloyd]

Hi,

Just wondering if anyone could advise on NexStar 6SE accessories and upgrades?

1. Power pack - I've seen the various options on the Maplin and Amazon websites (e.g. Jump Starters). Do these work properly and do you need to buy a cable separately as most appear to come with a 12v cable (although this appears to be for charging from a cigarette lighter - but it does appear that you could use the cable in reverse from the 12v output on the pack to the power jack on the scope).

Examples I've seen are :-

http://www.maplin.co.uk/3-in-1-portable-jumpstarter-383992

http://www.amazon.co.uk/Silverline-234578-Watt-Starter-Compressor/dp/B001C85UG8/ref=sr_1_1?ie=UTF8&qid=1355397825&sr=8-1

http://www.amazon.co.uk/Clarke-900-Start-Engine-Starter/dp/B004M3V8XY/ref=sr_1_2?ie=UTF8&qid=1355397839&sr=8-2

And also one in Halfords: http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_180830_langId_-1_categoryId_255206

....Or are you safer with a Skywatcher / Celestron Power Tank?

2. Diagonal - Is it worth replacing the stock Celestron diagonal that comes with the scope? If so, what are the recommended options?

3. Low power eyepiece (around 32mm). Can any NexStar owners advise on a suitable 32mm eyepiece? Not looking to spend the earth here (and don't think you probably need to for a low power view on an F/10 scope)?

[Capricorn]

People seem to use whatever power pack is on offer at the time, so there appears to be little to choose between them.

Be aware that they use a standard small lead acid battery and if they are run down and drain then the plates get damaged and they fail. They are pretty small and so drain reasonably fast, also we tend to carry on observing or imaging until we run out of power. So a drained power pack and a fair possibility that a new one is then required.

Concerning power to the scope, check but I thought that Celestron had a non-standard size centre pin, so you can get poor or intermittant contact at times. I think the "trick" was to bend the pin a little, however that can also snap the pin and then you are in a mess.

Diagonal, no real idea. Unless pretty poor you may not realise a great difference. Again if you decide to change then look for any that are on offer, like many items they vary in cost fairly dramatically. I see FLO do a 1.25" WO Diagonal at £65, usually WO products are good.

Decent low power eyepiece, for the SCT try the Vixen NPL plossl range, they do a 30mm at £40.

[greglloyd]

Thanks. Saw those WO diagonals on FLO (45 and 90 degree models) but just not sure if you would see £40 to £65 worth of a difference. It says they give increased brightness over the stock models. My diagonal is the Celestron 94115-A. Views through the scope are superb already, but if I thought a better diagonal would give an even better view then I would upgrade.

Have also seen the Vixen plossls. I currently have two X-Cel LX eyepieces with 60 deg FOV. Would the Plossls give a smaller FOV than the X-Cel LX eyepieces given the scope is an SCT? Or do I not get the 60 deg FOV out of the X-Cel LX eyepieces anyway?

If anyone can give a specific recommendation for a power pack / jump starter that they know is good with the Celestron NexStar scopes I'd appreciate hearing about it. Also whether you had to buy a cable to connect it to the scope or whether the supplied cables could be used.

[Dunkster]

It's hard to quantify the benefit without experimenting yourself really. You've got a new diagonal there so unless the screws bother you, the Celestron diagonal is probably sufficient. One idea might be to keep an eye on astro buy and sell for a dielectric one with compression rings at a decent price. I use a 2" SCT diagonal with mine (shared with my C8) as I like to use my 20mm Nagler without fear of it hitting the ground

The maplin power tank is quite popular and there's no good reason it shouldn't be ok with your 6SE. You will need a suitable 12v cable though.

Regarding FOV... there are 2 different FOVs to consider here:

...apparent field of view, aFOV, is how wide (or not) the view looks through the eyepiece. A lower number looks narrower, like looking through a straw, whereas higher numbers are wider and give a more immersive experience. At the same magnification, a wider aFOV EP will show you more sky at once

...true field of view, TFOV, is the size of the patch of sky your telescope is showing, with a given EP. Higher numbers = more sky.

There is somewhat of an approximate relationship between them.... TFOV ~= aFOV / magnification . Therefore with any telescope, lower magnification with result in seeing more sky, higher magnifications less.(There is a more precise relationship between the TFOV and field stop of the EP that I'll skip here!)

So in the case of the typical plossl compared with the X-Cel LX (assuming the EPs have the same focal length) the LX is showing you 20% wider view (but actually more than that proportion of sky because the view is a circular area). You will absolutely get the greater aFOV from your LX. SCTs tend to have long focal lengths, so we need to use longer FL EPs and/or wider aFOV EPs to get the widest views our telescopes are capable of, by way of their physical limitations... in the case of the 6SE, the limitation is imposed by the diameter of the baffle tube of 27mm. This happens to be the maximum field stop of 1.25" EPs, I'm sure not entirely by coincidence and works out at just over 1 degree TFOV.

Anyhow, achieving a little over 1 degree TFOV can be achieved using different combinations of FL and aFOV EPs, for example...

32mm 50 degree (plossl)

24mm 68 degree "super wide" angle (Panoptic, Hyperion or similar)

20mm 82 degree "ultra wide" angle (Nagler, Meade UWA or similar)

I'm sure you get the picture

[greglloyd]

Yep, thanks for that. So basically you've given me the answer I need. At 32mm (which is the focal length I am looking at) a plossl eyepiece with a 50 deg AFOV will give me as much TFOV as is possible with the scope and there is little need to look at wider AFOV eyepieces at that focal length, right?

If I decide to replace the 25mm eyepiece supplied with the scope, then choosing a super wide 68 degree AFOV eyepiece such as the Hyperion will again give me the max TFOV I can get from this scope?

Thanks for the advice!

[Dunkster]

It's not quite as simple as that.... it's essentially the same patch of sky only presented in different ways. The higher magnifications from the shorter FL ways of achieving this result in darker background sky and great contrast. For people like me in poor LP zones, there are often thresholds beyond which the level of skyglow impacts the view, so the magnification is useful then. But also the wider aFOV is also a different visual experience that's worth trying once to see if you like it.

This also overlooks differences in optical qualities and their performance of the different eyepiece designs. Unsurprisingly, there are some appealing qualities to the pricier examples that in some part justify their price tag. One thing I'd suggest is to go along to a local astro club if there is one as folk there should no doubt have a variety of kit to experience

A 24mm Hyperion (for example) would make the 25mm essentially redundant (besides for alignment?), but if you like plossls then the 32mm would give you the max.

Incidentally, you can increase the TFOV of the scope with a focal reducer (the Celestron one in particular for this scope) as it effectively reduces the FL of the scope to about 950mm, but I have no experience of these.

[greglloyd]

I've actually had quite a range of eyepieces before. With my last scope (10" Dob) I used to have a Skywatcher Panaview 32mm (2") which gave some very wide views. Also had Meade Series 5000 14mm which was a nice mid power eyepiece. Previously I also owned some Televue Plossls which gave quality views with 50 degree AFOV. It was noticeable that they FOV was not a wide, but they were nice eyepieces with sharp images.

I'm actually not that bothered with wide views with this new scope. I didn't buy it for that purpose as I'm now using decent binos for wide views of the North American Nebula and other large objects. Just wanting to make sure that the eyepieces I choose for this particular design of scope give them max FOV possible since I'm more used to choosing eyepieces for F5 scopes.

LP is not a problem here with limiting magnitudes varying from +6 to +8 depending on just how transparent the skies are on a particular night, so I get great contrast no matter which focal length I choose for eyepieces.

Regarding the 24mm eyepiece making the stock 25mm redundant - that would exactly be the intention - providing the Hyperion's 68 degree FOV would give better FOV than the stock eyepiece's 50 degrees. Otherwise, I wouldn't bother changing at this focal length.

Thanks for your advice

[Dunkster]

My apologies, wasn't my intent to patronise so I hope I didn't

Bins + SCT are a great combination for sure! SCTs with their long focal length are pretty forgiving with EPs, but it's tough to beat TV Plossls I've used one in my scope (too much sky glow from home ) but I've not tried a Hyperion, but feedback is generally very positive with SCTs. With dark skies such as yours, maybe the simpler optical solution would win?

For absolute widest, the Celestron fr/cc http://www.firstligh...al-reducer.html will eek you out to about 1.3 degrees (there was a thread on CN about this a while back that I'll try to dig out), but due to the sharper light cone you're pretty much restricted to a 22mm or so field stop before vignetting.

[greglloyd]

Hi Dunkster,

You definitely didn't patronise! Sorry if my reply came across that you had

My previous reply was just to advise that most of my previous eyepieces have been reasonably wide field and I do appreciate the wider FOVs that you get from the non-plossl designs.

After doing a bit of reading through some older threads I decided to complement my two existing X-Cel LX eyepieces with another two (9mm and 25mm). That gives me the following range of powers :-

7mm (214x)

9mm (167x)

12mm (125x)

25mm (60x)

That just leaves a gap to fill around (80x to 90x) which I can fill at a later date with the 18mm model.

[Dunkster]

Phew! That's OK then glad I didn't mess it up

The X-Cel LX should be great to excellent in your 6SE - as I'm sure you've read, folks use them in much more demanding scopes. 60 degrees is a nice comfortable aFOV and the bonus of staying with the range is they're parfocal There's also a 5mm for those exceptional nights, but you might be better off with a Barlow for greater flexibility.

[greglloyd]

I actually bugged out slightly on the 9mm and ended up placing the order for a 18mm and 25mm.

I decided that I'd probably get more use from the 18mm than from the 9mm - given that I already have 12mm (125x) and 7mm (214x).

I'm actually using the 7mm on Jupiter this evening and getting good views with it. Currently watching the GRS transit.

Thinking that the 18mm (83x) will get more use in the short term for smaller DSO's and I can still play with 125x and 214x on planets. Down the line I want something in between these two powers for nights were the seeing does not allow above 200.

[red dwalf]

i had a 6" sct and now have a 8" version, i did buy a 1.25" william optics diagonal and did a comparison test out in the field and the william optics was a much better view in my opinion compaired to the stock diagonal, it gave a brighter reflection and made the stock diagonal look dull, i`ve now upgraded that to a 2" william optics and would not change it.

as for power tanks, i`ve used a few, including the maplins one, but i`ve now ended up with a leisure battery which works better as they are used to being charged lots of times without problems, and copes with dew heaters and so on.

[SBC]

The maplin jump starter comes with a suitable cable for connecting to the scope and it is reduced at the moment. I have one and it works a treat.

[greglloyd]

Thanks SBC. You've swayed me towards it :-) my local branch has quite a few in stock so will pop in later this week.

[greglloyd]

p.s. Is the model you are using the one that is reduced to £24.99 at the mo? (The first one I linked to). Thanks

[SBC]

Yes it is the one reduced to £24.99. It has a cigarette lighter type socket on the side and the cable that come with the unit fits the scope power socket. The battery is 7Ah and the scope draws 075 A according to the manual I have, so the battery should last for hours.

[greglloyd]

Great. Thanks