APO refractor for HEQ5 (imaging)

[chaffingbuttock (Matthew)]

Hi guys,

have been searching for ages on the interweb for a good apo refractor to purchase to go with my not-yet-arrived HEQ5. I found one that I liked a lot and was reasonably affordable, only to find that it was much too heavy for the mount for imaging purposes :/

I was looking at this one: http://explorescientific.com/telesco...mm_ed_apo.html

There is the smaller 102mm one which is half the weight. And so, I have a dilemma.. get the smaller aperture one, or get something like the ED120 sky watcher, which apparently is a lot lighter (around 5.2kg for the OTA). My guess is that the ES one is much heavier because of the third lens and maybe more sturdier body construction. Can anyone recommend anything else in the 5 inch range that would be good for some imaging that isn't going to break the bank (i.e. takahashi etc)? I'm not sure about the benefits of triplet Vs doublet, since some doublets use FPL53 glass and some triplets use a central FPL51 glass.

Cheers.

[Larryp (Laurie)]

Hi Matthew,
Explore Scientific apos are just rebadged North Group. You would save money buying direct from them.

[LewisM]

I had a Northgroup ED127...

For a week...

[chaffingbuttock (Matthew)]

Lewis : that's not exactly a vote of confidence haha.

Laurie: thanks for the heads up. I tried a quick google search, but couldn't find anyone that stocked the north group branded ones. There was a really good price on the 127 triplet in the states for us$1700. I couldn't find another 5 incher in that price bracket.

I've spent the better part of today in front of the 'puter looking for a larger apo refractor that will be light enough for the HEQ5. At the moment, it seems like it's either a 5 inch doublet or a 4 inch triplet based on weight. It seems that the HEQ5 is good for about 7-8kg for photography, so minus my camera (0.3kg) and the finder scope etc bits and bobs, I think I could get away with maybe a 6-7kg scope. The alternative is I buy one of those EdgeHD 800 SCTs, since that seems to be about that weight and the reports seem to be pretty positive. I think I'd prefer a refractor though, cause it'd be more versatile for me and there's less hassle with maintenance.

[Larryp (Laurie)]

Just google North Group, and you can buy direct from the factory in China. Their focusers are not up to scratch, but its a simple matter to upgrade to a Moonlite or Feathertouch.
I'm very happy with my North Group 102mm-once I replaced the focuser with a Moonlite!

[chaffingbuttock (Matthew)]

There's also a chinese brand called sharpstar which seems to supply teleskop service and astrotech. they have up to 4 inch too.. I wonder how much they are and if they sell direct. Taobao has them for about au$1200 (minus all the fees etc)

[LewisM]

Just remember, Meade and Explore Scientific big refractors are all Northgroup. I think Altair may be too?

[MortonH]

Maybe the new Meade 115mm triplet from Bintel?

http://www.bintel.com.au/Telescopes/...oductview.aspx

[chaffingbuttock (Matthew)]

I saw the meade one. it's only usd$1999 in the states - i'll be heading there in a couple months so if i can pick one up there for cheap(er), that'd be nice.

I can't for the life of me find this northgroup company. Does it still exist? The closest I can find is one called hioptic. I even went to the northgroup.cn site which I followed from an email someone had posted in these forums and that doesn't exist.

http://www.hioptic.com/telescopes/

In any case, these guys don't have a 4 incher.

Interesting about the meade refractors.. they got a really good write up from what i saw. good optics. just gotta find north group now

[Larryp (Laurie)]

Just looked at the invoice for my scope, and it gives 2 email addresses.
gilman@northgroup.cn and hioptic@hotmail.com
If you Google "Nanjing instrument technology group", this is North group. For some reason it doesn't come up now if you google north group.

[chaffingbuttock (Matthew)]

so it sounds like they are called hioptic now. I'll get in touch with them but am also considering the sharp star one if its similarly priced. I want to get as big as the heq5 can take without breaking the bank and so long the imaging is good.

[Visionoz (Bill)]

Originally Posted by chaffingbuttock

.... It seems that the HEQ5 is good for about 7-8kg for photography, so minus my camera (0.3kg) and the finder scope etc bits and bobs, I think I could get away with maybe a 6-7kg scope. ....

Bear in mind that the quoted capacity is the the maximum --- as a general rule of thumb for astro-imaging you would like to load the mount to around only 70% max of its rated capacity (as far as Chinese-made mounts are concerned) thus you do have to allow aro 4-5kg max for all your OTA, bits & bob etc

Although I have seen some others pile up their mounts to the max and beyond and still take good images!!

YMMV as they say

HTH
Cheers
Bill

[chaffingbuttock (Matthew)]

Yep, some sites say the rated maximum it's 18kg and others say 14. In any case, I figure I can safely get about 8 kg on there unless others' experience say otherwise? I don't think it will allow for a 5 inch though, or at least it would be pushing it

[chaffingbuttock (Matthew)]

Ok, so now I'm confusing myself.. can anyone who has an heq5 chime in on how much they can stack on the mount for imaging please? some people are saying don't go over 50% max weight, some say 75%.. some people saying heq5 can do 14kg and others 18kg. even more people saying that they're pushing max weight for imaging, but it's all about being balanced in 3 axis and they're still able to get 20 minute subs guided. I'm still really keen on the ES 127 ED (or generic) and it says it's 9.9kg with all accessories, so throw in my camera (0.3kg) and a T-ring and I'll be below 10.5kg still. 10.5kg is exactly 75% of 14kg. I don't want to invest in a big scope and then find out that I can't use it though. help!

[RobC (Rob)]

I have an HEQ5 and have loaded a 7KG North Group Carbon Fibre ED 127 and a 3.5 KG North Group ED 80 together with a Cannon DSLR, guide camera and horizontal mounting bar adding about another 2.5 Kg for a total load weight of 13 KG. I conterbalanced this with 10KG. So this represents an all up weight of 23 kg.

Suprisingly it is easy to balance and guides perfectly. I am only a beginner imager but have had no problems doing 25 three minute exposures of different objects.

One thing I have noticed is that if I touch the mount it takes about 5 seconds to stop vibrating. My gut feeling is that this maybe due to the fact that the counter weight rod is fully extended with 10KG on the end.

There doesn't appear to be a definitive answer to this question. Most of of the sales literature states an all up weight of 13kgs that includes counter weights. So I am running 10KG over the stated maximum.

I purchased the HEQ5 PRO in November 2008 and never used it until this year. Back then it came standard with 10KG of counter weights. Now it comes standard with 5 KG of counter weight.

Hope this helps.

Regards Rob