Im­age Pro­cess­ing

An­i­ma­tions and sur­face sta­bil­i­sa­tions in PIPP

Sky at Night Magazine - - CONTENTS - MARTIN LEWIS is a So­lar Sys­tem astro im­ager and te­le­scope builder

An­i­ma­tions and sur­face sta­bil­i­sa­tions in PIPP.

Build a se­quence of shots to cre­ate a video of your favourite as­tro­nom­i­cal tar­get

We’re tak­ing an­other look at the free­ware astro video pro­cess­ing pro­gram PIPP (https://sites.google.com/

site/as­tropipp), the key fea­tures of which we cov­ered in our Au­gust and Oc­to­ber 2017 is­sues. In our pre­vi­ous in­stal­ments, we dis­cussed some of its ba­sic edit­ing func­tions; this month, we’re look­ing at how to com­bine your stills to­gether into an an­i­ma­tion and sta­bilise sur­face fea­tures on videos of the Sun and the Moon.

PIPP is able to con­vert video be­tween a num­ber of for­mats and read­ily split videos into in­di­vid­ual frames. Con­ver­sion the other way around – that is, tak­ing frames and stitch­ing them to­gether to make an an­i­ma­tion – is just as easy. You might want to do this to show the

evo­lu­tion of a so­lar promi­nence, the ro­ta­tion of a planet or the move­ment of its moons.

The first step in mak­ing an an­i­ma­tion is to add your set of frames to the list in the Source Files tab us­ing the Add

Im­age Files but­ton. When you select mul­ti­ple frames, the Join func­tion di­a­log box will pop up. Click Ok to link all the frames to­gether. If the files aren’t in the cor­rect or­der for the an­i­ma­tion, you can shuf­fle them by click­ing on the col­umn head­ers – name, date and so on. Al­ter­na­tively, you can select in­di­vid­ual frames in the list and move them around us­ing the up/down but­tons. The next step is to go to the Out­put

Op­tions tab and de­cide if you want to have a GIF or AVI an­i­ma­tion. In most

cases GIF is most ap­pro­pri­ate, as they al­low you to set the an­i­ma­tion to re­peat in­def­i­nitely by tick­ing Loop Frames

Re­peat­edly. On this tab you can also set the GIF’s qual­ity and the de­sired frame rate. In­ci­den­tally, the frame rate op­tion can be used for any video, al­low­ing for slower or faster play­back speed than the orig­i­nal record­ing – a use­ful func­tion, es­pe­cially for cre­at­ing time­lapses.

Op­tions and ad­just­ments

Other an­i­ma­tion re­lated op­tions are avail­able on the An­i­ma­tion Op­tions tab, and these in­clude the op­tion to in­tro­duce pauses at start or end of the se­quence, and to de­ter­mine for­ward and re­verse play­ing. Once you have set all the op­tions use the >

> Start but­ton in Do Pro­cess­ing tab to then cre­ate your an­i­ma­tion.

An­other valu­able PIPP fea­ture al­lows you to ad­just the gain (bright­ness) and gamma (con­trast) of all the frames of your recorded video. This is great for bring­ing out de­tails in footage such as all-sky cam­era time­lapses or overly dark lu­nar drift videos. The gain and gamma con­trols are found in the top-left of the Pro­cess­ing

Op­tions tab. To pre­view their ef­fect on a frame, use the Test Op­tions but­ton at the up­per-right cor­ner of PIPP.

PIPP is adept at suc­cess­fully align­ing and sta­bil­is­ing lu­nar and so­lar videos so that dif­fi­cult and jumpy videos can then work suc­cess­fully in stack­ing pro­grams such as Au­toStakkert! and RegiS­tax. It will cope well with sud­den po­si­tional changes due to pauses in the record­ing or sud­den wind buf­fet­ing that might cause is­sues for the stack­ing pro­grams with­out edit­ing. To align a so­lar or lu­nar video, click on

Sur­face Fea­tures in the Pro­cess­ing Op­tions tab and select Sur­face Fea­ture Track­ing and Sur­face Sta­bil­i­sa­tion. An ‘an­chor fea­ture box’ (AFB) will au­to­mat­i­cally ap­pear in the pre­view im­age which will be the first frame of the video. You should drag the mid­dle of the AFB onto a high-con­trast fea­ture such as a crater or sunspot and re­size it by drag­ging the cor­ners of the AFB un­til it fits the out­line of the cho­sen fea­ture.

Smooth­ing out wrin­kles

A nice re­fine­ment for lu­nar and so­lar videos is that you can also set an ‘area of in­ter­est’ (AOI) for the video by click­ing on the AOI box. This pro­duces a box that ev­ery frame must con­tain, or else the frame is re­jected. The use of an AOI pre­vents is­sues where the fi­nal stack might be­come a patch­work of dis­sim­i­lar ar­eas around the edge, each where dif­fer­ent num­bers of frames have contribute­d to them. The dif­fer­ent re­gions re­quire dif­fer­ent amounts of pro­cess­ing and this can cre­ate an­noy­ing arte­facts at their junc­tions.

You can po­si­tion and re­size the AOI box just like the AFB box, with the han­dles or via nu­mer­i­cal en­try. Do be aware that if the box is made too large you might find there are hardly any frames left which have not been re­jected for not con­tain­ing the AOI.

A fi­nal fea­ture that may be use­ful is PIPP’s abil­ity to per­form loss­less com­pres­sion us­ing the ULRG codec avail­able on the

Out­put Op­tions tab. This can be used for archiv­ing pur­poses and re­duces file sizes by about 30 per cent. Don’t worry, ULRG files can still be read by RegiS­tax and Au­toStakkert!, should you want to re­pro­cess them at a later date. S

Select the frames you want to use to make your an­i­ma­tion in the Source Files tab; do­ing so brings up this di­a­log box to merge them to­gether

PIPP also al­lows you to ad­just gain and gamma – in this case for an all-sky time­lapse

Set­ting AFBs (red) and AOIs (blue) will help with frame align­ment and re­duce stack­ing arte­facts

You can set frame rate and GIF loop­ing on the Out­put Op­tions tab

An­i­ma­tion op­tions in­clude adding pauses and play­back di­rec­tion

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